Fix sanity check --no* BoolOpts
Fix sanity check --no* BoolOpts

If --config-{file,dir} are used to genearate a list of tests to
run, using set_override() will also override any options passed
via the CLI.

For example, on Centos 7 which uses dnsmasq 2.66, running:

  neutron-sanity-check --nodnsmasq_version --config-file \
    /etc/neutron/l3_agent.ini

will still run and fail the dnsmasq version test. Using
set_default() allows using --config-{file,dir} and --no* in
conjunction.

Closes-Bug: #1549394
Change-Id: I5b9e520add7324660148c4451bbef54c0dfe428e

mahak/neutron,igor-toga/local-snat,wolverineav/neutron,huntxu/neutron,huntxu/neutron,sebrandon1/neutron,MaximNevrov/neutron,noironetworks/neutron,klmitch/neutron,cloudbase/neutron,mahak/neutron,eayunstack/neutron,noironetworks/neutron,bigswitch/neutron,wolverineav/neutron,bigswitch/neutron,igor-toga/local-snat,eayunstack/neutron,mahak/neutron,cloudbase/neutron,klmitch/neutron,openstack/neutron,openstack/neutron,sebrandon1/neutron,openstack/neutron,MaximNevrov/neutron