adb: Avoid waiting for emulator connections

This change exempts the emulator connections from
WaitableConnection.WaitForConnection(). This is because emulator
connections are a) more reliable and b) handled a bit differently than
normal TCP connections.

Bug: 78991667
Test: emulator -showkernel ; adb shell
Change-Id: I552946198889a82d6c265f45e8c3b38f6ac9d045

adb/transport.cpp

@@ -1040,6 +1040,11 @@ int register_socket_transport(int s, const char* serial, int port, int local) {
     auto waitable = t->connection_waitable();
     register_transport(t);
 
+    if (local == 1) {
+        // Do not wait for emulator transports.
+        return 0;
+    }
+
     return waitable->WaitForConnection(std::chrono::seconds(10)) ? 0 : -1;
 }