Export kernel-version to metadata

This exports the kernel version and ebuild rev to metadata.

For example it will set kernel-version for a board to "3.14-r1722".

BUG=None
TEST=cbuildbot_run_unittest
Trybot

Change-Id: I1a1086da34148285e4c03289975651eec4d3d583
Reviewed-on: https://chromium-review.googlesource.com/434223
Commit-Ready: Bernie Thompson <bhthompson@chromium.org>
Tested-by: Bernie Thompson <bhthompson@chromium.org>
Reviewed-by: Bernie Thompson <bhthompson@chromium.org>
(cherry picked from commit e454ce07d0b21575d40d2d8469e35c96cafea28b)
Reviewed-on: https://chromium-review.googlesource.com/442209
Commit-Queue: Bernie Thompson <bhthompson@chromium.org>
1 file changed