Make RDE SSH key identity injectable

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=133883090

javatests/google/registry/rde/RdeUploadActionTest.java

@@ -181,6 +181,7 @@ public class RdeUploadActionTest {
       action.ghostryde = new Ghostryde(BUFFER_SIZE);
       action.jsch =
           JSchModule.provideJSch(
+              "user@ignored",
               keyring.getRdeSshClientPrivateKey(), keyring.getRdeSshClientPublicKey());
       action.jschSshSessionFactory = new JSchSshSessionFactory(standardSeconds(3));
       action.response = response;