logaggregator: Use retry dialer in client
logaggregator: Use retry dialer in client

This prevents errors like the on in CI build
https://ci.flynn.io/builds/20151115010657-73c9f645 where the test got a
connection refused as it was connecting to a logaggregator which just
went down (but whose address was still being returned by discoverd).

Signed-off-by: Lewis Marshall <748e1641a368164906d4a0c0e3965345453dcc93@lmars.net>

philiplb/flynn,lmars/flynn,philiplb/flynn,benbjohnson/flynn,lmars/flynn,flynn/flynn,lmars/flynn,lmars/flynn,benbjohnson/flynn,philiplb/flynn,benbjohnson/flynn,benbjohnson/flynn,lmars/flynn,flynn/flynn,philiplb/flynn,flynn/flynn,flynn/flynn,flynn/flynn,benbjohnson/flynn,benbjohnson/flynn,philiplb/flynn