BUG/MINOR: unix: remove the 'level' field from the ux struct

BUG/MINOR: unix: remove the 'level' field from the ux struct

Commit 290e63aa moved the unix parameters out of the global stats socket
to the bind_conf struct. As such the stats admin level was also moved
overthere, but it remained in the stats global section where it was not
used, except by a nasty memcpy() used to initialize the ux struct in the
bind_conf with too large data. Fortunately, the extra data copied were
the previous level over the new level so it did not have any impact, but
it could have been worse.

This bug is 1.5 specific, no backport is needed.

Reported-by: Dinko Korunic <dkorunic@reflected.net>