One thing that bothers me regarding the new ImapStore is that there is no
tests to verify if the way how getImapId() uses a vendor policy hasn't changed.
This part is hard to test with a real vendor policy, and it can easily be
overlooked even if it's broken.
This CL offers ImapStoreUnitTests a way to test the interaction between
getImapId() and a vendor policy.
Also fixed a bug in VendorPolicyLoaderTest where it assumed the test apk
package name is "com.android.email.tests", but it may actually be
"com.google.android.email.tests" now. (Broken since the test makefile
used inherit-package.)
Change-Id: I8feb616ea28cb5cae5b4fba57e363771014ac599
