daemon: Accept G_MAXSSIZE as a known 'unlimited' memory limit

It seems like 3.10.x kernels produce unlimited memory limits
like this:

$ cat memory.limit_in_bytes
9223372036854775807

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
daemon: Don't enumerate cgroups that contain slashes

Due to a completely broken json-glib generation of JSON. See:

http://bugzilla.gnome.org/show_bug.cgi?id=727593

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
daemon: Don't require cgroups in both memory/cpuacct

Don't require a cgorup to be in both memory and cpuacct before we
start monitoring information in either of those places.

Once both cgroups disappear, then we consider the cgroup to be
gone.

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>