The default HAProxy timeout values are fairly strict. On a busy cloud
it is common to exceed one or more of these timeouts. The only
indication that HAProxy has exceeded a timeout and dropped the
connection is errors such as "BadStatusLine" or "EOF." These can be
very difficult to diagnose when intermittent.

This charm-helpers sync pulls in the change to update the default
timeout values to more real world settings. These values have been
extensively tested in ServerStack. Configured values will not be
overridden.

Partial Bug: #1736171

Change-Id: I973962a5c1538b0d9afbebea8cebf50d938ecfb5