Restore 'LCB_COMPRESSION' in the environment

This is currently needed as a workaround for a bug in the server (see
MB-11365)

Change-Id: I6179e60b002aef3dd716c72972d974719f09f76a
Reviewed-on: http://review.couchbase.org/38092
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>