Disable metadata service detection in the emulator. (#6860)

* Disable metadata service detection in the emulator.

Fix for #6765. The latest version of google-gax attempts
to read from the metadata server (on an internal IP address).
Setting the environment variable METADATA_SERVER_DETECTION=none
by default will turn this behavior off. This is overridable with
.env.local.

* changelog

Author: inlined

CHANGELOG.md

@@ -0,0 +1 @@
+Inject an environment variable in the node functions emulator to tell the google-gax SDK not to look for the metadata service. (#6860)

src/emulator/functionsEmulator.ts

@@ -1349,6 +1349,7 @@ export class FunctionsEmulator implements EmulatorInstance {
       cwd: backend.functionsDir,
       env: {
         node: backend.bin,
+        METADATA_SERVER_DETECTION: "none",
         ...process.env,
         ...envs,
         PORT: socketPath,
@@ -1451,7 +1452,6 @@ export class FunctionsEmulator implements EmulatorInstance {
   /**
    * Gets the address of a running emulator, either from explicit args or by
    * consulting the emulator registry.
-   *
    * @param emulator
    */
   private getEmulatorInfo(emulator: Emulators): EmulatorInfo | undefined {