LXC: Fix return code evaulation in lxcCheckNetNsSupport()

Commit b9dd878f (util: make it easier to grab only regular command exit)
changed the call semantics of virCommandRun() and therefore of virRun()
too. But lxcCheckNetNsSupport() was not updated.
As consequence of this lxcCheckNetNsSupport always failed and broke LXC.

Signed-off-by: Richard Weinberger <richard@nod.at>

src/lxc/lxc_driver.c

@@ -1475,8 +1475,7 @@ static int lxcCheckNetNsSupport(void)
     const char *argv[] = {"ip", "link", "set", "lo", "netns", "-1", NULL};
     int ip_rc;
 
-    if (virRun(argv, &ip_rc) < 0 ||
-        !(WIFEXITED(ip_rc) && (WEXITSTATUS(ip_rc) != 255)))
+    if (virRun(argv, &ip_rc) < 0 || ip_rc == 255)
         return 0;
 
     if (lxcContainerAvailable(LXC_CONTAINER_FEATURE_NET) < 0)