LU-5932 tests: load sunrpc module before insmod ptlrpc_gss

LU-5932 tests: load sunrpc module before insmod ptlrpc_gss

Lustre ptlrpc_gss module depends on Linux kernel sunrpc module.
This patch fixes load_module() in test-framework.sh to load the
sunrpc module before loading ptlrpc_gss module by using insmod.

This patch is back-ported from the following one:
Lustre-commit: 92479eca2ed5e1871b2660af280917e4d61bdba8
Lustre-change: http://review.whamcloud.com/12790

Signed-off-by: Jian Yu <jian.yu@intel.com>
Change-Id: I105608d37c5889def0fab938a249c2f2a8f2186f
Reviewed-on: http://review.whamcloud.com/13017
Tested-by: Jenkins
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Wei Liu <wei3.liu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>