AURORA-599 - Reset changelog and version for 0.5.0 rc2

Resets the CHANGELOG and .auroraversion back to state it was
before 0.5.0-rc1 was cut. Jira fixVersion fields have been updated
as well to match any recent resolved tickets since 0.5.0-rc1
was cut that did not get tagged correctly.

Bugs closed: AURORA-599

Reviewed at https://reviews.apache.org/r/23876/