selftest: samba-ktest-mit also needs $ENV{KRB5RCACHETYPE} = "none"

selftest: samba-ktest-mit also needs $ENV{KRB5RCACHETYPE} = "none"

We need to pass --mitkrb5 to selftest.pl in all cases we use
system mit kerberos not only when we also test the kdc.

We can't use a replay cache in selftest verifies the stat.st_uid
against getuid().

BTW: while debugging this on ubuntu 22.04 I exported
KRB5_TRACE="/dev/stderr", which means we get tracing into
the servers log file and into selftest_prefix/subunit for the client...

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>