Correct improper comment
Correct improper comment

"Delete server before trying to create server" looks confusing,
the author may would have wanted to say "Delete server before
trying to create image".

Change-Id: Ia0f8ca29d6042d022cf4f6edf60f149f4a5f9154

Juniper/tempest,vedujoshi/tempest,cisco-openstack/tempest,cisco-openstack/tempest,openstack/tempest,Juniper/tempest,masayukig/tempest,vedujoshi/tempest,masayukig/tempest,openstack/tempest