[NEXUS-6086] Only process events about jars in repositories that have P2 metadata capability enabled

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Merge pull request #224 from sonatype/NEXUS-6086-avoid-opening-jars-p2

[NEXUS-6086] Only process events about jars in repositories that have P2 metadata capability enabled