software/slaprunner: egrep accepts a path as argument.

So avoid spawning "cat" only for this.
Also, variable expansion quoting.

software/slaprunner/buildout.hash.cfg

@@ -31,7 +31,7 @@ md5sum = 9db9957f452bda370cb2d5cc2e833e85
 
 [template-runner-export-script]
 filename = template/runner-export.sh.jinja2
-md5sum = aba6f56ad7ba9e177aed5fcfcb90d926
+md5sum = bbe59ef9544322d34d45d34b875dbc4e
 
 [instance-runner-export]
 filename = instance-runner-export.cfg.in

software/slaprunner/template/runner-export.sh.jinja2

@@ -89,7 +89,7 @@ fi
 
 sleep 5
 sha256sum "$backup_directory_path" | sort -k 66 > "$tmp_backup_sum"
-cat {{ directory['backup'] }}/backup.signature | egrep "instance/slappart.*/srv/backup/" > $tmp_filtered_signature
+egrep "instance/slappart.*/srv/backup/" "$backup_directory/backup.signature" > "$tmp_filtered_signature"
 
 # If the diff fails, then the notifier will restart this script
 if diff "$tmp_backup_sum" "$tmp_filtered_signature"; then