Add the new to octopus call for subvolume snapshot info. Two fields
appear to return strings "yes"/"no", so could possibly have been
converted to booleans. In the chance that other string values get
returned and simplicity I left them as strings. If we need to, we can add
convenience funcs to return bools later.
Signed-off-by: John Mulligan <jmulligan@redhat.com>