To ensure the module exists, first load it. Then when we try to unload
the module (to check that our modprobe interface works), we will not get
spurious failures due to -ENOENT (in this case meaning the module did
not exist):

(vgem_basic:18361) igt-core-DEBUG: Starting subtest: unload
(vgem_basic:18361) igt-kmod-DEBUG: Could not remove module vgem (No such file or directory)
Test requirement not met in function test_unload, file vgem_basic.c:331:
Test requirement: module_unload() == 0
Last errno: 2, No such file or directory

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Petri Latvala <petri.latvala@intel.com>