rgw: don't return data within the librados cb

Fixes: #7030
The callback is running within a single Finisher thread, thus we
shouldn't block there. Append read data to a list and flush it within
the iterate context.

Reviewed-by: Sage Weil <sage@inktank.com>
Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: fix use-after-free when releasing completion handle

Backport: emperor, dumpling
Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Add backward comptible acting set until all OSDs updated

Add configuration variable to override compatible acting set handling.
Later we'll check the osdmap that all OSDs are updated to use new acting sets.

Fixes: #6990

Signed-off-by: David Zafman <david.zafman@inktank.com>
Reviewed-by: Samuel Just <sam.just@inktank.com>
(cherry picked from commit 19cff890eb6083eefdb7b709773313b2c8acbcea)
osd: Fix assert which doesn't apply when compat_mode on

Signed-off-by: David Zafman <david.zafman@inktank.com>
Reviewed-by: Samuel Just <sam.just@inktank.com>
(cherry picked from commit edaec9a8361396bd4c12814c16610669694b5b6c)
Merge remote-tracking branch 'gh/next'