Set reasonable defaults for new network values

Partially-implements blueprint better-support-for-multiple-networks

Change-Id: Ic9c60071480abc5fced04dab5fc79ea44db1e10d
Determine shared ip from table instead of flag

Partially-implements blueprint better-support-for-multiple-networks

Change-Id: Id7c6620704fef504d23cb42c5218251fa9e2dba7
Don't follow HTTP_PROXY when talking to localhost test server

Unlike urllib2, requests honours HTTP_PROXY by default.  This meant
test_uri_length_limit's test queries to http://localhost:$port/ would
hit the wrong localhost when $HTTP_PROXY was another host - resulting in a
meaningless test scenario and apparent failures with HTTP status codes
other than the expected REQUEST_URI_TOO_LARGE (414).

This change forces requests to go direct for those test queries.

Closes-Bug: #1329614
Change-Id: Ida3424ca9a750bd2d3f2e81dc7dfacc2a334adf1
Merge "Set reasonable defaults for new network values"
Merge "Determine shared ip from table instead of flag"
Merge "Don't follow HTTP_PROXY when talking to localhost test server"