CBQE-0: updating install.py and remote_util.py for xdcr_upr default. Additionally XDCR_USE_OLD_PATH variable was introduced in 3.0 and not present in previous version's start-up scripts.

Change-Id: I0835efca95e77743697eabd29b0b57f1ffafa8db
Reviewed-on: http://review.couchbase.org/37678
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Tested-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>