The admin_thread one is too new to be in 2.6.2, it was merged later that week. It will presumably be in the next 2.6 merge. As for the others, I'm not sure why they weren't taken. We took another RADOS_KV change from that same merge window. The last 3 aren't actually functional changes, just code re-org and debug messages, so they aren't very important (except for making other backports easier). But the "fix append" one is an actual bug fix and should probably be taken.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2019:0020