pylint: run coding-checks.sh with bash

[[ is a bash extension and therefore not
available on platforms where sh is not bash.
Use bash explicitly.

Change-Id: I3f31acd5fc3d7422270be53510962dcbc08db602

tools/coding-checks.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 set -eu