Sort plugins alphabetically

Better than file ordering, which is undefined. This way, they always run
in the same order.

Change-Id: I18b65665e0fd99aba953cae4959edd2a364b6031
Reviewed-on: https://gerrit.causes.com/23519
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Greg Hurrell <greg@causes.com>
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>