Clean up test keys in KeyAgreementTest

KeyAgreementTest was leaving test keys hanging around in keystore.
Clean them up after the tests run.

Additionally, delete the keys "just in case" before the tests run.
This way, no test accidentally sees a key hanging around from a prior
test that may not have exited properly.

Test: KeyAgreementTest
Change-Id: I4b50c995f5d2bc4e9b5a323a82b4565e52204bf1
1 file changed