[autotet] Pipe bug_template through control data.

Teach the control file parser to understand a new type of control
file variable, the bug template.

BUG=chromium:310859
TEST=Ran a suite and verified that control_data is available
     in dynamic_suites.

Change-Id: I91be1ff9b7f9771ec26f734f70386e7f7f8a3c2c
Reviewed-on: https://chromium-review.googlesource.com/192534
Tested-by: Prashanth B <beeps@chromium.org>
Reviewed-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Alex Miller <milleral@chromium.org>
Commit-Queue: Prashanth B <beeps@chromium.org>
2 files changed