dbt should reset adapters in handle_and_check

[beckjake]

Issue

dbt does not reset adapters during handle_and_check and multiple invocations result in an invalid cache.

Issue description

if you import dbt and used it to run multiple invocations in a row from the same process space, the adapters (and therefore cache) will be re-used. The cache makes some optimizations about what to track based on dbt's run ordering guarantees, and those guarantees aren't valid across multiple invocations.

Results

dbt made wrong assertions about the state of the world and crashed.

System information

dbt 0.12.1, all OSes

Steps to reproduce

• from dbt.main import handle_and_check
• handle_and_check(args1)
• handle_and_check(args2)

Where args1/args2 are things like ['run'] and ['archive'].

[beckjake]

Fixed in #1144