Upgrade protobuf-java from 2.5.0 to 2.6.0

From RPM discussion (BPMSPL-282)
Productization: protobuf-java redhat version is: 2.6.0-redhat-1, is it ok to upgrade from 2.5.0->2.6.0?

Motivation:

• The 2.5 version isn't build from source by productization, there is no redhat version.
• The 2.6 version is, which means they can do security patches on it easily (= important for long term support) and it can be RPM'ed (important for BPMSPL-282, which has PM support)
• 2.6 is higher than 2.5, so in theory this is low-risk change.

Needed on both master and 6.4.x.