X neotest: info-local: Fix it when CPU frequence/idle information is not available

For example under KVM it was failing as

    cpu:	Intel(R) Xeon(R) CPU E5-2678 v3 @ 2.50GHz
    cat: /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq: No such file or directory
      File "<string>", line 1
        print '%.2fGHz' % ( / 1E6)
                            ^
    SyntaxError: invalid syntax

    $ lscpu
    Architecture:        x86_64
    CPU op-mode(s):      32-bit, 64-bit
    Byte Order:          Little Endian
    Address sizes:       40 bits physical, 48 bits virtual
    CPU(s):              40
    On-line CPU(s) list: 0-39
    Thread(s) per core:  1
    Core(s) per socket:  1
    Socket(s):           40
    NUMA node(s):        1
    Vendor ID:           GenuineIntel
    CPU family:          6
    Model:               63
    Model name:          Intel(R) Xeon(R) CPU E5-2678 v3 @ 2.50GHz
    Stepping:            2
    CPU MHz:             2494.238
    BogoMIPS:            4988.47
    Virtualization:      VT-x
    Hypervisor vendor:   KVM
    Virtualization type: full
    L1d cache:           32K
    L1i cache:           32K
    L2 cache:            4096K
    L3 cache:            16384K
    NUMA node0 CPU(s):   0-39
    Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl xtopology cpuid tsc_known_freq pni pclmulqdq vmx ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm invpcid_single pti tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid xsaveopt arat

-> Fix it by checking whether cpufreq/cpuidle directories are available, and display "?" if they are not.

go/neo/t/neotest

 #!/bin/bash -e
 # neotest: run tests and benchmarks against FileStorage, ZEO and various NEO/py and NEO/go clusters
 
-# Copyright (C) 2017-2018  Nexedi SA and Contributors.
+# Copyright (C) 2017-2020  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -640,15 +640,20 @@ system_info() {
 	freqstable=y
 	while read cpu; do
 		f="$cpu/cpufreq"
-		fmin=`fkghz $f/scaling_min_freq`
-		fmax=`fkghz $f/scaling_max_freq`
-		fs="`cat $f/scaling_driver`/`cat $f/scaling_governor` [$fmin - $fmax]"
+		if ! test -d "$f"; then
+			fs="?"
+			freqstable=n
+		else
+			fmin=`fkghz $f/scaling_min_freq`
+			fmax=`fkghz $f/scaling_max_freq`
+			fs="`cat $f/scaling_driver`/`cat $f/scaling_governor` [$fmin - $fmax]"
+			test "$fmin" != "$fmax" && freqstable=n
+		fi
 		if [ "$fs" != "$freqstr" ]; then
 			freqdump
 			freqstr="$fs"
 		fi
 		freqcpuv+=(`basename $cpu`)
-		test "$fmin" != "$fmax" && freqstable=n
 	done \
 	< <(ls -vd $syscpu/cpu[0-9]*)
 	freqdump
@@ -656,16 +661,20 @@ system_info() {
 	latmax=0
 	while read cpu; do
 		is="`cat $sysidle/current_driver`/`cat $sysidle/current_governor_ro`:"
-		while read state; do
-			is+=" "
-			lat=`cat $state/latency`
-			res=`cat $state/residency 2>/dev/null` || res="?"	# added in linux 3.15
-			test "`cat $state/disable`" = "1" && is+="!" || latmax=$(($lat>$latmax?$lat:$latmax))
-			is+="`cat $state/name`·${lat}/${res}"
-		done \
-		< <(ls -vd $cpu/cpuidle/state[0-9]*)
-
-		is+=" # elat/tres µs"
+		if ! test -d "$cpu/cpuidle"; then
+			is+=" ?"
+		else
+			while read state; do
+				is+=" "
+				lat=`cat $state/latency`
+				res=`cat $state/residency 2>/dev/null` || res="?"	# added in linux 3.15
+				test "`cat $state/disable`" = "1" && is+="!" || latmax=$(($lat>$latmax?$lat:$latmax))
+				is+="`cat $state/name`·${lat}/${res}"
+			done \
+			< <(ls -vd $cpu/cpuidle/state[0-9]*)
+
+			is+=" # elat/tres µs"
+		fi
 
 		if [ "$is" != "$idlestr" ]; then
 			idledump