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-1219 Let multiverse run for Resque + JRuby
RUBY-1219 Don't defer Resque startup if can't fork

We typically defer startup of the agent until the before_first_fork hook in
Resque so we can catch if the master process daemonizes. On JRuby we don't
install the before_first_fork hook, though (since we can't fork), but we also
defer startup.

Instead, skip deferring if we're on a platform that can't fork.
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
Fix fake collector for pruby vs JSON

Some results passed to the fake collector on pruby versions of the agent
weren't quite what it expected.

Properly unblob the tree traces, and handle the symbol->string translation for
hashes.
RUBY-1152 Standardize on merge! as method name for merging data back into containers
RUBY-1152 Standardize on reset! as the method to drop data from containers
RUBY-1152 Pull reset! out of harvest on RequestSampler

reset! just resets, but harvest also records supportability metrics about the
number of samples seen vs. recorded.
RUBY-1152 Move RulesEngine setup from specs into RulesEngine class
RUBY-1152 Move metric_rules from Agent to StatsEngine (all harvest methods now take no args)
Merge pull request #239 from newrelic/resque_test_fix

Fix fake collector for pruby vs JSON
Merge pull request #237 from newrelic/RUBY-1219

RUBY-1219 Don't defer Resque startup if can't fork
RUBY-1219 Follow-up - fix pipe channel manager tests for JRuby