BUG/MINOR: ocsp: Crash when updating CA during ocsp updates

BUG/MINOR: ocsp: Crash when updating CA during ocsp updates

If an ocsp response is set to be updated automatically and some
certificate or CA updates are performed on the CLI, if the CLI update
happens while the OCSP response is being updated and is then detached
from the udapte tree, it might be wrongly inserted into the update tree
in 'ssl_sock_load_ocsp', and then reinserted when the update finishes.

The update tree then gets corrupted and we could end up crashing when
accessing other nodes in the ocsp response update tree.

This patch must be backported up to 2.8.
This patch fixes GitHub #3100.

(cherry picked from commit 257df69fbdcff5c1feb3b24a4cf6141f86984447)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit f885845e2b2c50996d3373eb5d2e84d3e7fcfbb8)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 7a2c66c5e90e2f69ba59dbdc6818e1f2dba27f41)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>