NEO: use stack/slapos.cfg versions for cffi/gevent/greenlet

This fixes build of gevent on recent OS, due to missing greenlet
header file for Python 2.

software/neoppod/stress-testing/software.cfg

@@ -78,8 +78,6 @@ packages +=
   ca-certificates file g++ libc6-dev make patch python
 # speed up build by using the following components from the OS
   git liblzma-dev libssl-dev pkg-config python-dev
-# for pygolang
-  python-greenlet-dev
 # extra requirements for NEO
   libnetfilter-queue-dev nftables
 # extra requirements for this SR

software/neoppod/stress-testing/stress.cfg

@@ -41,9 +41,6 @@ command =
   [versions]
   slapos.cookbook =
   NetfilterQueue = 0.8.1
-  greenlet = 0.4.15
-  gevent = 1.3.7
-  cffi = 1.11.5
   # use the following components from the OS
   # and don't build dependencies for nothing
   [git]