virLockManagerNopInit: Rename flags to unused_flags

As these might be not used and make syntax-check complains about checking
them via virCheckFlags.

src/locking/lock_driver_nop.c

@@ -29,10 +29,10 @@
 
 static int virLockManagerNopInit(unsigned int version ATTRIBUTE_UNUSED,
                                  const char *configFile ATTRIBUTE_UNUSED,
-                                 unsigned int flags ATTRIBUTE_UNUSED)
+                                 unsigned int flags_unused ATTRIBUTE_UNUSED)
 {
     VIR_DEBUG("version=%u configFile=%s flags=%x",
-              version, NULLSTR(configFile), flags);
+              version, NULLSTR(configFile), flags_unused);
 
     return 0;
 }