Handle changes of tools or pom.xml, ignore doc/pom.xml

https://review.openstack.org/#/c/49888/ introduces doc/pom.xml, we
should not check that file or use it for building.

This showed also books were not build since changes to pom.xml
were ignored.

Additionally, we now build all books whenever some special files
are touched like test.py or doc/pom.xml.

Change-Id: I6e074587093735294f88462db97d398a1ad2e384