initscripts fkt: Fix shebang

We use features only available in bash. So we should state correctly
that the script should be executed in bash. As sh is a symlink to bash
this makes not differences on a ipfire system. But my linter is less
chatty with this change.

Signed-off-by: Jonatan Schlag <jonatan.schlag@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

src/initscripts/system/functions

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 ###############################################################################
 #                                                                             #
 # IPFire.org - A linux based firewall                                         #