Bumping up max_length of flavor extra spec.

The capture field in the flavor extra spec form, is currently set to 25,
but should be bumped up to accommodate some long values.

Change-Id: I54a12b01222faf0d7dd32768c73f192e3d3cf8e1
Fixes: bug #1252427
Merge "Bumping up max_length of flavor extra spec."