API-7698: Fix possible issue with connection becoming stalled after interrupt during call.execute

[sbogolii-sift]

Purpose

Our customer experiences SocketTimeoutException with sift-java.
Overall it looks like this is still an open issue with okhttp.

Technical details

Seems, When using Call.execute() which is synchronous, the actual initial request processing including writing to the HTTP/2 socket is done on the calling thread, so an interrupt leaves the HTTP/2 connection in an inconsistent state.

Workarounds:

1. set the connectionPool in the builder so it uses a new connection pool w/ a size of zero
2. turn off HTTP/2 support by setting a new protocolList in the builder with only HTTP/1.1 support.

Another workaround with implementation proposed -
always use enqueue, even to simulate an execute so the thread writing the underlying socket is never a user thread that can be interrupted.

Seems this is the most optimal fix, and will be implemented in this PR.
With the current fix siftClient. enqueueRequests() will use enqueue instead of execute

[sbogolii-sift]

/jenkins-test