harness: Use destination strncpy() expression for sizeof() argument
Even though this is the same size, as the sizeof() is derived from the
source expression, recent gcc versions will emit a warning, which is
turned into an error by -Werror:
error: argument to ‘sizeof’ in ‘strncpy’ call is the same expression
as the source; did you mean to use the size of the destination?
[-Werror=sizeof-pointer-memaccess]
Signed-off-by: Guillem Jover <guillem@hadrons.org>
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>