admin: Tiny cleanups
    
    First hunk changes the use of srcdir to top_srcdir so it complies with
    other rules in the Makefile.  Second one removes the need of
    remote_protocol.h in admin_protocol.h as it was suggested and worked in,
    but this one line was missed apparently.  Last one just removes the
    'remote' naming from admin protocol specification, just so it's cleaner.
    
    Signed-off-by: Martin Kletzander <mkletzan@redhat.com>