Bug 2112768

.Users can now drain hosts that are listed in explicit placements Previously, draining hosts that were listed as part of an explicit placement would cause the hosts not to be properly drained and tracebacks would be logged until the drain was stopped or hosts were removed from any explicit placement . With this fix, the handling of explicit placements is implemented internally and `cephadm` is able to determine if it needs to remove daemons from the hosts. Consequently, users can now drain hosts that are listed as part of an explicit placement without having to first remove the host from the placement. However, users still need to remove the host from any explicit placement before removing the host fully or specifications that explicitly list the host cannot be applied.