libpam / xtests: remove bash dependency

libpam / xtests: remove bash dependency

There's not bash specific syntax in the xtests scripts:

  $ cd Linux-PAM-1.1.6/xtests
  # replace /bin/bash to /bin/sh and check the bashisms:
  $ checkbashisms *.sh
  No output

So the runtime dependency to bash could be removed.

(From OE-Core rev: 1917bf7aa74aa1b86756c73c56537db2591115e5)

Signed-off-by: Wenzong Fan <wenzong.fan@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>