nss: Stop using one DBus interface with totally different methods
    
    This is an incorrect use of DBus, where we use a single interface
    name with completely different sets of methods.
    
    Easily fixed.
    
    Once the vtable stuff is in use then this would be automatically
    detected and fail to build.
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
    Reviewed-by: Sumit Bose <sbose@redhat.com>
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
    Reviewed-by: Simo Sorce <simo@redhat.com>
    (cherry picked from commit 3e7d7af1953410f3f009bf3b2e481a46fb80de83)