Fix wrong migrations

For Postgres migrations are failed.
More then we can get for mysql an error
"Specified key was too long; max key length is 1000 bytes" in b6ae66d05e3
migration in some versions of dialect.

Fixes-Bug: #1219776

Change-Id: Id9b0e1eb0e685053291367f7eb62fef68b6b2f84
Clean-ups related to alarm history patches

Some non-blocking clean-ups requested in reviews of the alarm
history patches.

Change-Id: If009166be450f2e1bba0e68ce74699b5a032543e
nova_notifier: fix tests

The prototype for instance_update_and_get_original changed, so let's
ignore it completely for the future.

Change-Id: Icfa161109e76e2717f64084ddce829f6c68aeb57
Fixes-Bug: #1221173
Merge "Fix wrong migrations"
Merge "Clean-ups related to alarm history patches"
add MAINTAINERS file

add MAINTAINERS file to list specialist maintainers for unique
components of ceilometer

Change-Id: I0622d735935f1eae34542b782beae317416e230c