Change alarm_history.detail to text type

The existing alarm_history.detail column size is 255 chars,
which is not enough for some large JSON payloads.

Change to Text column to make sure we store all detail.

Closes-Bug: #1236861
Signed-off-by: Stephen Gran <stephen.gran@guardian.co.uk>
(cherry picked from commit 57eb9e904aacae166d7265a914960415c57cd133)

Change-Id: I1460c2a5bbd5cb465a605bb80775853468148026
Merge "Change alarm_history.detail to text type" into milestone-proposed