fix(mdraid): add grow continue service

During raid assembly mdadm will call mdadm-grow-continue.service if
reshape is in progress.
If service doesn't exist then it is done via fork and systemd will kill
it unconditionally after processing all events.

Add proper service to allow systemd to manage reshape correctly.

Signed-off-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>

modules.d/90mdraid/module-setup.sh

@@ -136,6 +136,9 @@ install() {
         if [ -e $dracutsysrootdir$systemdsystemunitdir/mdadm-last-resort@.timer ]; then
             inst_simple $systemdsystemunitdir/mdadm-last-resort@.timer
         fi
+        if [ -e $dracutsysrootdir$systemdsystemunitdir/mdadm-grow-continue@.service ]; then
+            inst_simple $systemdsystemunitdir/mdadm-grow-continue@.service
+        fi
     fi
     inst_hook pre-shutdown 30 "$moddir/mdmon-pre-shutdown.sh"
     dracut_need_initqueue