Add create & attach times to SolidFire attributes.

Add create & attach times to SolidFire attributes.

This change simply adds create_time and attach_time to
the SolidFire devices attributes.

Times are taken from the volume-ref object, attach_time
is only set/present after an attach, and is also removed
from the attributes list on a detach.

This also required that we actually set attach_time on the
volume in the db.  We have the column, but we weren't actually
setting it, so this change required that be fixed.

In the future we should also look at changing the attach_time
from a string to a proper date-time object.

Change-Id: Ib9577ac160596a6878d1729f6022885b6cfa90e2