LP1744386: Alphabetize stat cats in volcopy attr editor

LP1744386: Alphabetize stat cats in volcopy attr editor

To test:
1. Go to the volume copy editor.  Confirm that the stat
cats do not display in order of owning library or stat cat
name.
2. Apply this commit.
3. Go to the volume copy editor.  Confirm that the stat
cats now display in alphabetical order by owning library,
then stat cat name.

Signed-off-by: Jane Sandberg <sandbej@linnbenton.edu>
Signed-off-by: Jason Etheridge <jason@EquinoxInitiative.org>