update version to 1.2.1-SNAPSHOT
Revert "update version to 1.2.1-SNAPSHOT"

This reverts commit 654aa9a9f337e5cc87c11e22b4554aadeb8f098c.
update version to 1.2.1-SNAPSHOT.
fix MOHO-75 when unjoining, should wait until peer.unjoin().get() complete.