cereal should check for enabled sessions other than by looking for links in /var/service

[jrollins]

as is, cereal determines running sessions by looking for /var/service/cereal.*. however, this is not an accurate representation of active sessions, since a session could have been stopped with sv stop /var/service/cereal.host, one would not be able to attach to it, and it would still show up in cereal as active.

This issue actually points to the fact that there are actually more session states than we're indicating (with the SFLAG):

• created
• linked
• running

right now a session starting a session links and starts it, but testing for running only looks to see if it's linked.

[jrollins]

Created a new SFLAG, '!', that indicates that the session is linked, but not running (ie. in an "odd" state). However, this is only indicated for users that can read the session supervise directory.

We therefore also added a new /etc/cereal/cereal-admin.conf config file that can be used to specify whether or not new session are created with world accessible supervise directories or not (may be a security risk on systems where FIFO file permissions are not respected).

These changes are implemented in 0.9-1.

[jrollins]

actually, the changes are implemented in 0.10-1.