Only pass in CLA name to the CLA hook

Previously we were passing in the entire CLA, only to get the
name.  While for most objects it might be better to pass in
more info, for the CLA, this data is currently unused.
Simplifying this makes it easier to eventually define a new
CLA Event in the extension points, and then to port the hooks
to use this new extension point listener.  If this data is
needed at some later point, a new ClaInfo could be defined.

Change-Id: Ib8e8428acb2d3366e573d162a282516646609201

gerrit-server/src/main/java/com/google/gerrit/common/ChangeHookRunner.java

@@ -715,12 +715,12 @@ public class ChangeHookRunner implements ChangeHooks, EventDispatcher,
     }
 
     @Override
-    public void doClaSignupHook(Account account, ContributorAgreement cla) {
+    public void doClaSignupHook(Account account, String claName) {
       if (account != null) {
         List<String> args = new ArrayList<>();
         addArg(args, "--submitter", getDisplayName(account));
         addArg(args, "--user-id", account.getId().toString());
-        addArg(args, "--cla-name", cla.getName());
+        addArg(args, "--cla-name", claName);
 
         runHook(claSignedHook, args);
       }

gerrit-server/src/main/java/com/google/gerrit/common/ChangeHooks.java

@@ -154,7 +154,7 @@ public interface ChangeHooks {
   public void doTopicChangedHook(Change change, Account account,
       String oldTopic, ReviewDb db) throws OrmException;
 
-  public void doClaSignupHook(Account account, ContributorAgreement cla);
+  public void doClaSignupHook(Account account, String claName);
 
   /**
    * Fire the Ref update Hook

gerrit-server/src/main/java/com/google/gerrit/common/DisabledChangeHooks.java

@@ -59,7 +59,7 @@ public final class DisabledChangeHooks implements ChangeHooks, EventDispatcher,
   }
 
   @Override
-  public void doClaSignupHook(Account account, ContributorAgreement cla) {
+  public void doClaSignupHook(Account account, String claName) {
   }
 
   @Override