glibc: Skip 2 qemu tests that can hang in oe-selftest

glibc: Skip 2 qemu tests that can hang in oe-selftest

qemumips and qemuppc were leaving stale processes behind after
running glibc oe-selftest. During analysis, it was found that
it was due to "tst-scm_rights" and "tst-scm_rights-time64" tests.
Disable them so that there are no stale processes left behind.

[YOCTO #15423]
https://bugzilla.yoctoproject.org/show_bug.cgi?id=15423

Signed-off-by: Yash Shinde <Yash.Shinde@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>