Fix regression from commit 137e80cd86

Problem:

A false-negative in check-config.sh for cgroups v2 systems was fixed but the
commit introduced a regression based on a small assumption that content of
/sys/fs/cgroup/cgroup.controllers would have the same format as the content
of /proc/self/cgroup. It doesn't.

Solution:

This just tweaks the regex to count occurrences of either cgroup
subsystem-names on each line (as occurs in the sysfs pseudo-file), or those
names with colons either side (as occurs in the procfs pseudo-file).

Signed-off-by: Rowan Thorpe <rowan@rowanthorpe.com>

contrib/util/check-config.sh

@@ -341,7 +341,7 @@ case "${cgroupVariant}" in
         cgroupFile='/proc/self/cgroup'
         ;;
     esac
-    if [ "$(tr -s ' ' '\n' <"${cgroupFile}" 2>/dev/null | grep -Ec "^(${cgroupMatch})\$")" -eq ${cgroupMatchNum} ]; then
+    if [ "$(tr -s ' ' '\n' <"${cgroupFile}" 2>/dev/null | grep -Ec "(^|:)(${cgroupMatch})(\$|:)")" -eq ${cgroupMatchNum} ]; then
       cgroupStatus='good'
     else
       cgroupStatus='bad'