Add shebang to mark bash files

This helps editors like vim detect the appropriate syntax highlight.

Change-Id: If06ac8aec6c2c1ab3aee2df19e1c63c37eb30e76
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>

devstack/lib/mdev_samples

@@ -1,3 +1,5 @@
+#!/bin/bash
+
 function compile_mdev_samples {
     set -x
     local kver=$(uname -r)