Keystore 2.0: Reduce sqlite cache to 0.5M

The default sqlite cache size of 2M is excessive for keystore use cases.
Reduce it to avoid memory pressure on low memory devices.

Bug: 186436093
Test: atest CtsKeystoreTestCases, saw heap usage drop ~1M
Change-Id: I52e7d78ee15fe863857866848ede84e0f3e4f216
1 file changed