Fix CLEAR_IF_FIRST handling of messages.tdb

Fix CLEAR_IF_FIRST handling of messages.tdb

We now open messages.tdb even before we do the become_daemon. become_daemon()
involves a fork and an immediate exit of the parent, thus the
parent_is_longlived argument must be set to false in this case. The parent is
not really long lived :-)
(This used to be commit 4f4781c6d17fe2db34dd5945fec52a7685448aec)