dispatcher: avoid "dirname" and "basename" calls in "10-ifcfg-rh-routes.sh" script

The script is run for every dispatcher event. Most of the events are not
actually relevant, and we just need to determine that there is nothing
to do and quit.

Avoid calling "dirname" and "basename".

The supported ifcfg-file has a very specific form. We can just check
(and parse) it in one got regular expression in bash.

examples/dispatcher/10-ifcfg-rh-routes.sh

@@ -16,17 +16,13 @@ if [ "$2" != "pre-up" ] && [ "$2" != "down" ]; then
     exit 0
 fi
 
-dir=$(dirname "$CONNECTION_FILENAME")
-if [ "$dir" != "/etc/sysconfig/network-scripts" ]; then
-    exit 0
-fi
+file_regex='^/etc/sysconfig/network-scripts/ifcfg-([^/]+)$'
 
-profile=$(basename "$CONNECTION_FILENAME" | sed -ne 's/^ifcfg-//p')
-if [ -z "$profile" ]; then
-    exit 0
-fi
+[[ "$CONNECTION_FILENAME" =~ $file_regex ]] || exit 0
 
-if [ ! -f "$dir/rule-$profile" ] && [ ! -f "$dir/rule6-$profile" ]; then
+profile="${BASH_REMATCH[1]}"
+
+if [ ! -f "/etc/sysconfig/network-scripts/rule-$profile" ] && [ ! -f "/etc/sysconfig/network-scripts/rule6-$profile" ]; then
     exit 0
 fi