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>

lib/drmtest.c

@@ -224,7 +224,7 @@ int drm_get_card(void)
 }
 
 /** Open the first DRM device we can find, searching up to 16 device nodes */
-static int __drm_open_any(void)
+int __drm_open_any(void)
 {
 	for (int i = 0; i < 16; i++) {
 		char name[80];

lib/drmtest.h

@@ -71,6 +71,7 @@ static inline void *igt_mmap64(void *addr, size_t length, int prot, int flags,
 #define ALIGN(v, a) (((v) + (a)-1) & ~((a)-1))
 
 int drm_get_card(void);
+int __drm_open_any(void);
 int drm_open_any(void);
 int drm_open_any_master(void);
 int drm_open_any_render(void);