ci: fix 'crit.sh: 3: source: not found'

Jenkins test runs are failing with:

 ./test/jenkins/run_ct ./test/jenkins/crit.sh
 ./test/jenkins/crit.sh: 3: source: not found

Switch to bash which has 'source'.

Signed-off-by: Adrian Reber <areber@redhat.com>

test/jenkins/_run_ct

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 set -e
 mount --make-rslave /

test/jenkins/run_ct

@@ -1,3 +1,3 @@
-#!/bin/sh
+#!/bin/bash
 
 unshare --mount --pid --fork -- $(readlink -f `dirname $0`/_run_ct) "$@"