ctdb: open the RO tracking db with perms 0600 instead of 0000

ctdb: open the RO tracking db with perms 0600 instead of 0000

While 0000 is possible from the UNIX/POSIX point of view,
these permissions create problems in an environment with
selinux enabled, which is more strict.

This aligns the perms of the read only tracking db with other
internal dbs.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11577

Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
Autobuild-User(master): Amitay Isaacs <amitay@samba.org>
Autobuild-Date(master): Wed Oct 28 06:13:09 CET 2015 on sn-devel-104