Do not declare depends-maven-plugin in odlparent

This declaration is only used in SFT as far as I can tell. The plugin is quite dead upstream to the point of not having been updated for parallel builds (ODLPARENT-264).

Remove its declaration from odlparent/pom.xml, so downstreams are not tempted to use it.

There are a few downstream users:

ovsdb/southbound/southbound-it/pom.xml
ovsdb/hwvtepsouthbound/hwvtepsouthbound-it/pom.xml
controller/opendaylight/md-sal/mdsal-it-parent/pom.xml
infrautils/itestutils/parent/pom.xml
infrautils/caches/sample/it/pom.xml

all of which seems to point towards the need for better pax-exam integration.