run-command API users: use strvec_pushv(), not argv assignment

run-command API users: use strvec_pushv(), not argv assignment

Migrate those run-command API users that assign directly to the "argv"
member to use a strvec_pushv() of "args" instead.

In these cases it did not make sense to further refactor these
callers, e.g. daemon.c could be made to construct the arguments closer
to handle(), but that would require moving the construction from its
cmd_main() and pass "argv" through two intermediate functions.

It would be possible for a change like this to introduce a regression
if we were doing:

      cp.argv = argv;
      argv[1] = "foo";

And changed the code, as is being done here, to:

      strvec_pushv(&cp.args, argv);
      argv[1] = "foo";

But as viewing this change with the "-W" flag reveals none of these
functions modify variable that's being pushed afterwards in a way that
would introduce such a logic error.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>