sessions command doesn't work with ib_srpt

[agrover]

reported by @celesteking in #12.

Our current sessions cmd works by parsing the nodeacl info file in configfs. see https://github.com/open-iscsi/rtslib-fb/blob/master/rtslib/target.py#L922. One way to solve this would be change ib_srpt in the kernel to report sessions there, so targetcli/rtslib would pick it up without change. Or, we could do something in rtslib to get this info for srpt another way, but this may be difficult because we don't currently have an abstraction that would let us override NodeACL behavior for a particular fabric type.

[celesteking]

Just wondering, is ib_srpt exposing this info at all, by any means?