Temporarily disabled KeyManagementTest for automotive.

The keys generated by DO (which runs on user 0, in background) don't
match keys checked by PO (which is the current forefround user).

Test: atest com.android.cts.devicepolicy.MixedDeviceOwnerTest#testKeyManagement,testGenerateKeyPairLogged,testDelegatedCertInstallerDirectly,testSetKeyGrant,testSetKeyPairCertificateLogged # on automotive and phone
Bug: 184197972

Change-Id: I42c0fec0e6dfa5498c1354ae03b62eb4a6bb4d18