Switch hdp to cdh in the default list of Sahara plugins
Switch hdp to cdh in the default list of Sahara plugins

hdp is no longer enabled by default in Sahara, as of
https://review.openstack.org/284922 . It makes sense to remove it
by default in Tempest, to avoid failures when using default
configurations. Let's switch it to cdh, which is supported in
previous versions.

Change-Id: I7ab7fa89584c43104e5c3b297266e4641f6592a3

cisco-openstack/tempest,openstack/tempest,Tesora/tesora-tempest,vedujoshi/tempest,masayukig/tempest,Tesora/tesora-tempest,masayukig/tempest,LIS/lis-tempest,vedujoshi/tempest,Juniper/tempest,bigswitch/tempest,zsoltdudas/lis-tempest,zsoltdudas/lis-tempest,LIS/lis-tempest,sebrandon1/tempest,cisco-openstack/tempest,openstack/tempest,bigswitch/tempest,Juniper/tempest,sebrandon1/tempest