mw-teardown.sh: to be run after mw jobs

By using a postbuildscript publisher, we can execute an action after a
job has completed (regardless of the build status if needed). We will
invoke mw-teardown.sh which let us easily clear out files as needed.

Start by deleting the sqlite database created via mw-install-sqlite.sh

Bug: 71128
Change-Id: I16f8e5a44bf9dbf7244a64564e0aefb5a7eb2d91