ceph: ignore BrokenPipeError when printing help

ceph: ignore BrokenPipeError when printing help

ignore BrokenPipeError which is thrown when piping the output of ceph
CLI to a tool which might close its stdin before ceph CLI sends the
whole help message.

Follow approach suggested by Kefu: https://github.com/python/cpython/commit/7b0ed43af55c1e2844aa0ccd5e088b2ddd38dbdb
This doesn't manage the clean-up/exit logic, as that's deferred to the
last part of the __main__ code.

Fixes: https://tracker.ceph.com/issues/47400
Signed-off-by: Ernesto Puerta <epuertat@redhat.com>