Remove pause/unpause NotImplementedError API layer

There are 2 kinds of RPC call from API layer to compute layer,
one is cast and another is call. For cast, the RPC message will
be posted and the API service will not wait for the message to
be processed. So it won't be able to catch the exception raised
in compute layer, so catch and handle the exception is useless
and error leading. This patch removes code in API layer for
pause and unpause functions.

Change-Id: I7cbb8179b3eec8496b90ff5cf07397522d52c5de
Merge "Remove pause/unpause NotImplementedError API layer"