ceph-nvmeof-mon fixes

ceph-nvmeof-mon fixes

Resolves: rhbz#2280205

- NVMeofGwMonitorClient: assert gateway state does not vanish
  Signed-off-by: Alexander Indenbaum <aindenba@redhat.com>
- send unavailable in beacon response to gw that did not exit after failover
  Signed-off-by: Leonid Chernin <leonidc@il.ibm.com>
- fix blacklist start when osd is not writtable
  Signed-off-by: Leonid Chernin <leonidc@il.ibm.com>
- Clean up

  - NVMeofGwTypes: remove copied_nonce_map cleanup
  - NVMeofGwMon.h: fix weird spacing
  - NVMeofGwMon.cc: dout(4) to dout(10)
  - NVMeofGwMon.cc: rm commented out code

  Signed-off-by: Alexander Indenbaum <aindenba@redhat.com>
  (cherry picked from commit 05a7b1f31a87cd60c21cd46bbcde5c7745721f55)

Signed-off-by: Alexander Indenbaum <aindenba@redhat.com>
(cherry picked from commit bad3542358edaf950bfda49044e52ae5de757aa0)