Remove build-ami from the default admin jenkins.

Since this file changes rapidly in jenkins and it is difficult to manage
via version control here.  It's hard to maintain the changes made from
Jenkins in sync here, so remove it from git to reduce complexity.
Add boto credentials to jenkins.
Corrections and updates for boto template.
Add messages to fail messages.
Merge pull request #1226 from edx/feanil/generic_admin

Feanil/generic admin