dkms postinst: do not execute init script if it is not present yet.

From: Michael Prokop <mprokop@sipwise.com>

debian/ngcp-mediaproxy-ng-kernel-dkms.postinst

@@ -15,10 +15,12 @@ if [ "x${isadded}" = "x" ] ; then
 fi
 
 if [ "$1" = 'configure' ] ; then
-	dkms build -m "$name" -v "$version" && dkms install -m "$name" -v "$version" || true
+        dkms build -m "$name" -v "$version" && dkms install -m "$name" -v "$version" || true
 
-	# try to start the daemon
-	/etc/init.d/ngcp-mediaproxy-ng-daemon start || true
+        # try to start the daemon
+        if [ -x /etc/init.d/ngcp-mediaproxy-ng-daemon ] ; then
+                /etc/init.d/ngcp-mediaproxy-ng-daemon start || true
+        fi
 fi
 
 #DEBHELPER#