tests: Remove 'netdev-dpdk' unit test

There is only one unit test in these files and it no longer makes
sense in Open vSwitch 2.1.2 due to changes in the APIs. Remove it.

Change-Id: I05eff950764aa4ee1218b8efc9be4ace4e1809e6
Signed-off-by: Stephen Finucane <stephen.finucane@intel.com>
Reviewed-by: Ciara Loftus <ciara.loftus@intel.com>
datapath/dpdk: Change log level for some messages

Some usually-irrelevant log messages are being generated by during
normal operation, due to the changes made in '54b2f9d'. These messages
negatively impact performance during the normal use case. Change the
level of these log operations to only show at higher verbosity log
levels to fix this issue.

Change-Id: Ida26c7c016845d97b49c9ae65da3cdd627343eff
Signed-off-by: Stephen Finucane <stephen.finucane@intel.com>
Reviewed-by: Kevin Traynor <kevin.traynor@intel.com>
Reviewed-by: Ian Stokes <ian.stokes@intel.com>