bash: fix testcase run-coproc/run-execscript/run-test/run-heredoc failed

bash: fix testcase run-coproc/run-execscript/run-test/run-heredoc failed

Add user 'test' to fix the failure of 'the test suite should not
be run as root'(run-execscript and run-test)

Backport test case from git://git.sv.gnu.org/bash.git to fix run-execscript
and run-heredoc

Still failed cases:
FAIL: run-intl
FAIL: run-lastpipe
FAIL: run-trap

YOCTO: 5698

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>