[driver] fixing invalida_cache srv_open list traverse

instead of the srv_open list pointer we were incrementing the main loop
of fcb opens. it lead to an infinite loop when the srv_open list contained
more than 1 entry for a given fcb.

sys/nfs41_driver.c

@@ -6756,7 +6756,7 @@ VOID fcbopen_main(PVOID ctx)
 #endif
                         break;
                     }
-                    pEntry = pEntry->Flink;
+                    psrvEntry = psrvEntry->Flink;
                 };
             }
             nfs41_fcb = (PNFS41_FCB)cur->fcb->Context;