RUBY-1216 Ensure that we retry when the initial connect attempt fails

This behavior was previously broken with 75919097.

Agent#handle_server_connection_problem has been removed, since it seems to have
never been hit prior to 75919097, and is misleading.
RUBY-1217 Send threshold with copied TT's across pipe
Merge pull request #231 from newrelic/RUBY-1217

RUBY-1217 Send threshold with copied TT's across pipe
CHANGELOG for 3.6.8 patch release
Merge pull request #235 from newrelic/CHANGELOG_3.6.8.167

CHANGELOG for 3.6.8 patch release
RUBY-1221 Fix re-merging of analytics events upon a failed transmission
CHANGELOG entry for RUBY-1221
RUBY-1221 CHANGELOG updates for 3.6.8.168
Merge pull request #238 from newrelic/RUBY-1221

RUBY-1221 Fix re-merging of analytics events upon a failed transmission