admin: Tiny cleanups

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>