Unbreak tests that assert that 10,000 keys can be imported.

These Android Keystore tests time out on slower hardware. This CL
switches these tests from importing a fixed number of keys (10,000)
to importing as many as it can for a fixed amount of time (3 minutes)
and failing if fewer than 2,000 keys were imported.

Bug: 22299022
Change-Id: I39953f47bc91b0d3c9ceff89274b00c6e9d4fd65
1 file changed