=act #3525 Retry finishConnect after OP_CONNECT

Patch picked from https://github.com/spray/spray/commit/63648f17807035b4c17b5377ec67f5455a31e5a6
Merge pull request #1675 from akka/wip-finish-connect-retries-patriknw

=act #3525 Retry finishConnect after OP_CONNECT