driver: log missing modules as INFO, not WARN

Missing modules is a common expected scenario for most libvirt usage on
RPM distributions like Fedora, so it doesn't really warrant logging at
WARN level. Use INFO instead

https://bugzilla.redhat.com/show_bug.cgi?id=1274849

src/driver.c

@@ -62,7 +62,7 @@ virDriverLoadModule(const char *name)
         return NULL;
 
     if (access(modfile, R_OK) < 0) {
-        VIR_WARN("Module %s not accessible", modfile);
+        VIR_INFO("Module %s not accessible", modfile);
         goto cleanup;
     }