AURORA-392: Add apache- to source distribution name

Updates release scripts to prefix the package with Apache namespace.

Testing Done:
Performing dry-run....
apache-aurora-0.5.1-rc0-incubating.tar.gz         apache-aurora-0.5.1-rc0-incubating.tar.gz.md5
apache-aurora-0.5.1-rc0-incubating.tar.gz.asc     apache-aurora-0.5.1-rc0-incubating.tar.gz.sha

Bugs closed: AURORA-392

Reviewed at https://reviews.apache.org/r/21253/