Fix --remote option to replication start

Declaring --remote as a 'Set<String>' field trips args4j's
Setters.create(), which only treats List, Map, and Arrays as
multi-value containers. Use a method-based @Option that adds
each --remote value into a Set<String> to work around this.

Change-Id: Ic4b4242f3c9ac05b822f2b62141ba34270619f70
(cherry picked from commit 87a975dd6a62d383fc2d3914162365976123e1c2)

src/main/java/com/googlesource/gerrit/plugins/replication/StartCommand.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/StartCommand.java b/src/main/java/com/googlesource/gerrit/plugins/replication/StartCommand.java
index 74d46e1..92c619c 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/StartCommand.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/StartCommand.java
@@ -42,8 +42,12 @@
   @Option(name = "--url", metaVar = "SUBSTRING", usage = "substring URL must match (or * to match everything)")
   private String urlMatch;
 
+  private final Set<String> remotesToConsider = new HashSet<>();
+
   @Option(name = "--remote", metaVar = "REMOTE", usage = "name of remote to replicate to")
-  private Set<String> remotesToConsider = new HashSet<>();
+  void addRemote(String remote) {
+    remotesToConsider.add(remote);
+  }
 
   @Option(name = "--wait", usage = "wait for replication to finish before exiting")
   private boolean wait;