dracut-module-setup.sh: rework kdump_get_ip_route_field

Avoid duplicated echo / cut / grep call, just use sed.

Signed-off-by: Kairui Song <kasong@redhat.com>
Acked-by: Philipp Rudo <prudo@redhat.com>

dracut-module-setup.sh

@@ -523,9 +523,7 @@ kdump_get_ip_route()
 
 kdump_get_ip_route_field()
 {
-    if `echo $1 | grep -q $2`; then
-        echo ${1##*$2} | cut -d ' ' -f1
-    fi
+    echo "$1" | sed -n -e "s/^.*\<$2\>\s\+\(\S\+\).*$/\1/p"
 }
 
 kdump_get_remote_ip()