Change trove instance table name

To be consistent with other panels in
the dashboard we are renaming the trove
panels to use the term 'Instances'
instead of 'Databases' to represent the
top level Trove instance.

Change-Id: I30d2cfb82eeb7bf806dcf89e6a204a61a310f3ea
Closes-Bug: #1336492
Merge "Change trove instance table name"