Update instance's cell_name in API cell.

It was accidentally being removed before updating the DB due to code
being moved and not updated.  The test for the method was broken, too,
allowing this bug to sneak in.

Fixes bug 1098093

Change-Id: I05c00b8b100568b39afb8ee0ca7ee94d4dd97c0a
(cherry picked from commit abc9a0d5df70ee00ba38e655a4d88ae18417f0e3)
Merge "Update instance's cell_name in API cell." into milestone-proposed