Add functions to scan for multiple environment variables

This is needed for normalizing environment variables

Change-Id: I2ecf00357ed5bed21b642d6fc4e96ca705ce5a24
Reviewed-on: http://review.couchbase.org/38775
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>