net/py-lib389: pass the process environment when starting dirsrv

Extend the FreeBSD start patch so lib389 launches the ns-slapd process
with a copy of the current environment (env = dict(os.environ)) instead
of an empty one. This lets the Kerberos settings (e.g. KRB5_KTNAME) reach
the directory server process, which is required for GSSAPI/GSS-SPNEGO binds
on FreeBSD.

Sponsored by: Netzkommune GmbH