igt/drv_module_reload: Check more carefully for a live driver

As drm_open_any() now quietly fails if there is no driver, this
nullifies the effectiviness of using gem_exec_nop as the test for a good
reload. Combine with gem_alive (and guarantee that gem_alive can detect
a dead driver, putting lie to

commit 032f30cb38
Author: Thomas Wood <thomas.wood@intel.com>
Date:   Tue Jan 13 13:33:57 2015 +0000

    lib: remove unnecessary checks on the drm_open_any return value

) first.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88573
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

tests/gem_alive.c

@@ -14,7 +14,9 @@ int main(void)
 
 	signal(SIGALRM, SIG_IGN);
 
-	fd = drm_open_any();
+	fd = __drm_open_any();
+	if (fd < 0)
+		return IGT_EXIT_SKIP;
 
 	alarm(1);
 	if (ioctl(fd, DRM_IOCTL_I915_GEM_SW_FINISH, &arg) == 0)