network: Add coverity[leaked_handle] to ignore error

On error, the 'tapfd' in networkStartNetworkVirtual() is synonymous
with 'macTapIfName' and will be closed in the appropriate error path.

src/network/bridge_driver.c

@@ -2530,6 +2530,7 @@ networkStartNetworkVirtual(struct network_driver *driver,
         virSetError(save_err);
         virFreeError(save_err);
     }
+    /* coverity[leaked_handle] - 'tapfd' is not leaked */
     return -1;
 }