Add metrics for quota limits

[samuel-p]

Are there any plans to add metrics for Gluster Volume Quota Limits? I just saw you mentioned it in issue #3 some time ago.

I'm especially thinking of the output of the gluster volume quota list command:

# gluster volume quota my-vol list
                  Path                   Hard-limit  Soft-limit      Used  Available  Soft-limit exceeded? Hard-limit exceeded?
-------------------------------------------------------------------------------------------------------------------------------
/my-path                            1.0GB     80%(819.2MB)   0Bytes   1.0GB              No                   No
...

Thanks for this awesome project.

[aravindavk]

Any suggestions for labels and values?

glusterfs_quota_hard_limit{path="/my-path", hard_limit="1.0GiB"} <1 exceeded, 0 - not exceeded>
glusterfs_quota_soft_limit{path="/my-path", soft_limit="819.2MB"} <1 exceeded, 0 - not exceeded>
glusterfs_quota_used_bytes{path="/my-path", hard_limit="1.0GiB", soft_limit="819.2MB"} <used_bytes>
glusterfs_quota_available_bytes{path="/my-path", hard_limit="1.0GiB", soft_limit="819.2MB"} <available_bytes>