Allow HttpEngine to retry connections on timeout / interruption.

This reverts behaviour introduced in 60f5406dcc094d043 where HttpEngine
doesn't attempt to recover connections on timeout / interruption. This
new behaviour introduced regressions on some devices where we're handed
a mixture of IPV4 / IPV6 routes but where only one aspect of the network
(either IPV4 or 6) is functional.

bug: 22779586

(cherry picked from commit 34d6cda5)

Change-Id: I1036e4c1dbb29e72c0d07a491d49677936f3f154