MB-100: try to avoid using 127.0.0.1 as cbcollect_info directory

I.e. often nodes have 127.0.0.1 assigned. Which is common for single
node clusters.

We now detect 127.0.0.1 and attempt to pick interface that's used to
speak to internet.

Change-Id: Id4ca587db51b9b2deb1ba395a7ff3a921bb16fb8
Reviewed-on: http://review.couchbase.org/25708
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>