Fix failure with rbd on slow ceph clusters

Fix failure with rbd on slow ceph clusters

Make rados connection interval and retries configurable
for _try_remove_volume() function

Otherwise on slow ceph clusters, we can get following problem:

"ImageBusy error raised while deleting rbd volume. This may have been
caused by a connection from a client that has crashed and, if so,
may be resolved by retrying the delete after 30 seconds has elapsed."

Change-Id: I1230715663ea00c3eb4241154e6f194dee0e23d4
Co-Authored-By: Dirk Mueller <dirk@dmllr.de>
Closes-Bug: #1554045