As part of Terraform 0.7.1 it was observed in issue #8345 that the state
migration for google_compute_firewall did not appear to be running,
causing a panic when an uninitialized member was read. This commit hooks
up the state migration function (which _was_ independently unit tested
but was not actually in place).
There is currently no good test framework for this, I will address this
issue in a future RFC.
78a96f50bb