tap: fix possible fd leak in net_init_tap

In hotplugging scenario, taking those true branch, the file
handler do not be closed. Let's close them before return.
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

net/tap.c

@@ -796,6 +796,7 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
         if (net_init_tap_one(tap, peer, "bridge", name, ifname,
                              script, downscript, vhostfdname,
                              vnet_hdr, fd)) {
+            close(fd);
             return -1;
         }
     } else {
@@ -823,6 +824,7 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
             if (queues > 1 && i == 0 && !tap->has_ifname) {
                 if (tap_fd_get_ifname(fd, ifname)) {
                     error_report("Fail to get ifname");
+                    close(fd);
                     return -1;
                 }
             }
@@ -831,6 +833,7 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
                                  i >= 1 ? "no" : script,
                                  i >= 1 ? "no" : downscript,
                                  vhostfdname, vnet_hdr, fd)) {
+                close(fd);
                 return -1;
             }
         }