util: pidfile_pid() should not unlink PID file

util: pidfile_pid() should not unlink PID file

This causes a race.  If 2 callers to pidfile_create() both a find a
stale PID file using pidfile_pid().  The 1st may then return to
pidfile_create() and create a new PID file, which can then be unlinked
by the 2nd caller.

Consequently, PID file creation can not depend on creating the file,
so drop O_EXCL from the call to open().

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Volker Lendecke <vl@samba.org>