[autotest] Move imports of reporting to the function it's used.

reporting modules have dependency on external packages, e.g., httplib2
Such dependency can cause issue to any module tries to import suite.py
without building site-packages first. Since the reporting modules are
only used in this function, move the imports here avoid the
requirement of building site packages to use other functions in this
module.

One use case for this change is for brillo builders to run autotest
script to generate the suite control file mapping. The script needs to
import suite.py, but failed due to reporting has a dependency on the
site package httplib2.

BUG=None
TEST=run a suite, unittest

Change-Id: I8c611ee53164fa0c415e3eab945280a40255e081
Reviewed-on: https://chromium-review.googlesource.com/328014
Commit-Ready: Dan Shi <dshi@google.com>
Tested-by: Dan Shi <dshi@google.com>
Reviewed-by: Shuqian Zhao <shuqianz@chromium.org>
1 file changed