BUG/MINOR: filters: Skip disabled proxies during startup only

BUG/MINOR: filters: Skip disabled proxies during startup only

This partially reverts the patch 400829cd2 ("BUG/MEDIUM: filters: Don't try to
init filters for disabled proxies"). Disabled proxies must not be skipped in
flt_deinit() and flt_deinit_all_per_thread() when HAProxy is stopped because,
obvioulsy, at this step, all proxies appear as disabled (or stopped, it is the
same state). It is safe to do so because, during startup, filters declared on
disabled proxies are removed. Thus they don't exist anymore during shutdown.

This patch must be backported in all versions where the patch above is.