nevra: added _has_just_name helper method
nevra: added _has_just_name helper method

Closes: #189
Approved by: j-mracek

Conan-Kudo/libhif,hughsie/libhif,rpm-software-management/libhif,Conan-Kudo/libhif,rpm-software-management/libdnf,edynox/libdnf,edynox/libdnf,Conan-Kudo/libhif,edynox/libdnf,rpm-software-management/libhif,edynox/libdnf,hughsie/libhif,hughsie/libhif,rpm-software-management/libhif,rpm-software-management/libhif,Conan-Kudo/libhif,hughsie/libhif,rpm-software-management/libdnf,rpm-software-management/libdnf,rpm-software-management/libdnf