(maint) Refactor unit tests for Connector's monitor task
(maint) Refactor unit tests for Connector's monitor task

Using the same logic to test both blocking and non-blocking functions
that start the monitor task.

MikaelSmith/cpp-pcp-client,MikaelSmith/cpp-pcp-client,puppetlabs/cpp-pcp-client,MikaelSmith/cpp-pcp-client,MikaelSmith/cpp-pcp-client,puppetlabs/cpp-pcp-client,puppetlabs/cpp-pcp-client,puppetlabs/cpp-pcp-client,MikaelSmith/cpp-pcp-client