Change version rbenv-ruby to 1.9.3-p484 for nailgun

Bug: https://github.com/wayneeseguin/rvm/issues/2320
Partial-bug: #1294602
Change-Id: I8b376235eaa5701e99a7c9b8a28241f19965b19a
Merge "Change version rbenv-ruby to 1.9.3-p484 for nailgun"