ipatests: Specify shell implementation

The shell command line options and parameters used there are bash-
specific. This results in an error on attempting of running
'ipa-run-tests' on systems where '/bin/sh' is pointing to another
shell, for example, dash on Ubuntu.

Fixes: https://pagure.io/freeipa/issue/8101
Signed-off-by: Stanislav Levin <slev@altlinux.org>
Reviewed-By: Sergey Orlov <sorlov@redhat.com>

ipatests/ipa-run-tests

@@ -63,7 +63,7 @@ if not has_option("junit_family"):
 pyt_args = [sys.executable, "-c",
             "import sys,pytest;sys.exit(pytest.main())"] + sys.argv[1:]
 # shell is needed to perform globbing
-sh_args = ["/bin/sh", "--norc", "--noprofile", "-c", "--"]
+sh_args = ["/bin/bash", "--norc", "--noprofile", "-c", "--"]
 pyt_args_esc = [
     f"'{x}'" if not x or " " in x else x
     for x in pyt_args