contrib/check-config.sh: Remove awk dependency

The awk dependency is an issue when running check-config.sh on systems
without awk. The use of awk can be replaced with sed, which improves
portability.

The PR code review discussion iterated via grep to this final sed
version that is all Tianon Gravi's art.

Co-authored-by: Tianon Gravi <admwiggin@gmail.com>
Signed-off-by: Joakim Roubert <joakim.roubert@axis.com>

contrib/check-config.sh

@@ -163,7 +163,7 @@ printf -- '- '
 if [ "$(stat -f -c %t /sys/fs/cgroup 2> /dev/null)" = '63677270' ]; then
 	wrap_good 'cgroup hierarchy' 'cgroupv2'
 else
-	cgroupSubsystemDir="$(awk '/[, ](cpu|cpuacct|cpuset|devices|freezer|memory)[, ]/ && $3 == "cgroup" { print $2 }' /proc/mounts | head -n1)"
+	cgroupSubsystemDir="$(sed -rne '/^[^ ]+ ([^ ]+) cgroup ([^ ]*,)?(cpu|cpuacct|cpuset|devices|freezer|memory)[, ].*$/ { s//\1/p; q }' /proc/mounts)"
 	cgroupDir="$(dirname "$cgroupSubsystemDir")"
 	if [ -d "$cgroupDir/cpu" ] || [ -d "$cgroupDir/cpuacct" ] || [ -d "$cgroupDir/cpuset" ] || [ -d "$cgroupDir/devices" ] || [ -d "$cgroupDir/freezer" ] || [ -d "$cgroupDir/memory" ]; then
 		echo "$(wrap_good 'cgroup hierarchy' 'properly mounted') [$cgroupDir]"