This reverts commit 0b25a06a

Each thread has its own rados context. The thead pool, when used will allow better
parallelism of asynchronous requests.

This required some rework on the backend creations as the threads will need logging.

This will limit contention on the scheduling lock when there is no new mount to schedule (which
is the majority of the time).

Removed castor-rmc-server rpm from buildtree-stage1-rpms/Dockerfile because CTA now builds /usr/bin/cta-rmcd

mediachanger/castorrmc/CMakeLists.txt
mediachanger/castorrmc/common/CMakeLists.txt
mediachanger/castorrmc/rmc/CMakeLists.txt

Please note that casting the result to void is not good enough for gcc >= 7

Added -Wno-narrowing -Wno-implicit-fallthrough compiler flags to protoc3 output files if using gcc version 7 or greater

We now assume that Finished() will always be called, so explicit timeout
handling in RequestProc is redundant.

In case of successful Request processing, the XRootD framework will call
Finished(cancel=false). In the case of a failure or timeout, the framework
will call Finished(cancel=true).

Fixed errors generated by Scheduler code passing getMessage() instead of getMessage().str() to ScopedParamContainer.add()