hasKeyPair callable by the cred mng app

The credential management app can call
hasKeyPair. The provided alias must be
found in the credential management
app's authentication policy.

Bug: 177979648
Test: atest com.android.server.devicepolicy.DevicePolicyManagerTest
      atest android.devicepolicy.cts.CredentialManagementAppTest
Change-Id: Ib28549fb4e2848ba012df2d154d28f2002ec6e59