Install RestForwarderServletModule only if HTTP transport is used

Besides skipping installation of unnecessary servlets this change also
fixes an issue with Guice injection dependencies: the @RestGson is bound
(from the RestForwarderModule) only if the transport is REST. However,
the REST servlets now also depend on the @RestGson and, if another
transport is used where RestForwarderModule module is not installed,
then we have a missing dependency issue.

Change-Id: Id650bf9c4e5f723689f19d6e333afc059c95df66

src/main/java/com/ericsson/gerrit/plugins/highavailability/HttpModule.java

diff --git a/src/main/java/com/ericsson/gerrit/plugins/highavailability/HttpModule.java b/src/main/java/com/ericsson/gerrit/plugins/highavailability/HttpModule.java
index 921d750..e0c6061 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/highavailability/HttpModule.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/highavailability/HttpModule.java
@@ -33,7 +33,9 @@
 
   @Override
   protected void configureServlets() {
-    install(new RestForwarderServletModule(config));
+    if (config.main().transport() == Configuration.Transport.HTTP) {
+      install(new RestForwarderServletModule(config));
+    }
     if (config.healthCheck().enabled()) {
       install(new HealthServletModule());
     }