ovs_hex_dump() sometimes yields a trailing space in its output.  This is
annoying for the test infrastructure, since we have to specially mark the
trailing white space in Autotest with a "@&t@" marker at the end of the
line.  This commit gets rid of the trailing white space and the annoying
"@&t@" markers.

This also gets rid of an occasional trailing hyphen.

Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Russell Bryant <russell@ovn.org>