travis: Disable tests (but keep builds) on flaky distros
travis: Disable tests (but keep builds) on flaky distros

I went through the Travis history a bit, and these seem to be
the flaky ones.  The ubuntu one is likely no libsoup patches.
The other one @smcv has partially traced to a GPGME race condition
or something like that.

For the libsoup one; as I say in comments, once we have libcurl, I'd like to
enable that mostly everywhere, which should (hopefully) be more reliable.

Closes: #664
Approved by: cgwalters

GNOME/ostree,GNOME/ostree,GNOME/ostree,GNOME/ostree,GNOME/ostree