[ycabled][active-active] no initialize Async Client, when no active-a…

…ctive cable type; fix names for all ycabled threads (#373)

This PR intends to not start sonic-ycabled's Asynchronous client, when there is no active-active cable type.
The Problem that we encounter is ycabled expects all threads to be working/running state all the time.
Since there are no active-active cable_type Async client thread exits gracefully,
but by design this needs to be working if added to monitor loop thread. So this PR fixes this problem by runnig the Async Client only if configuration is active-active for atleast a cable.

This PR also has all the infrastructure changes UT for all Classes having infinite loops in ycabled, thus helping in picking up cases if changes break the code.

Signed-off-by: vaibhav-dahiya <vdahiya@microsoft.com>