Fixed RPM license linting error
Merge pull request #1199 from jamtur01/aslrpm

Fixed RPM license linting error.

Reviewing existing in-the-wild usage of rpm 'License' fields, nobody agrees on the correct thing to use. However, Redhat recommends "ASL 2.0" to mean "Apache License 2.0" (https://fedoraproject.org/wiki/Licensing:Main?rd=Licensing) so we will use that.
Merge git://github.com/logstash/logstash