Easy testrun level attachments

[Paul Sokolovsky]

lava_test_shell recently acquired lava-test-case-attach helper to easily do testcase-level attachments. It would be nice to do testrun-level attachments in the same vein.

In other words, I'd like to be able to add attachment to appear on a page like https://validation.linaro.org/lava-server/dashboard/streams/anonymous/cbuild/bundles/77c4d3a10ebbc425d85546b29a1f9baaf96aa3bf/e11de33e-37c8-11e2-9729-68b599be548c/ , not just for https://validation.linaro.org/lava-server/dashboard/streams/anonymous/cbuild/bundles/77c4d3a10ebbc425d85546b29a1f9baaf96aa3bf/e11de33e-37c8-11e2-9729-68b599be548c/result/1/

I actually though about patching lava-test-case-attach to do that for the case of missing/empty testcase name, but the script name kinda suggested about *testcase*, so I'm not sure if it's ok approach, or if should be separate script.

[Paul Sokolovsky (pfalcon)]

See also lp:1085989

[Michael Hudson-Doyle (mwhudson)]

This is easy enough, wasn't sure people would want it.