Added a UserManager.DISALLOW_AUTOFILL restriction.

bug: 35710740

Test: cts-tradefed run commandAndExit cts-dev -m CtsAutoFillServiceTestCases -t android.autofillservice.cts.LoginActivityTest#testUserRestriction
Test: cts-tradefed run commandAndExit cts-dev -m CtsDevicePolicyManagerTestCases -t com.android.cts.devicepolicy.MixedDeviceOwnerTest#testDisallowAutofill_allowed
Test: cts-tradefed run commandAndExit cts-dev -m CtsDevicePolicyManagerTestCases -t com.android.cts.devicepolicy.MixedProfileOwnerTest#testDisallowAutofill_allowed
Test: cts-tradefed run commandAndExit cts-dev -m CtsDevicePolicyManagerTestCases -t com.android.cts.devicepolicy.MixedManagedProfileOwnerTest#testDisallowAutofill_allowed

Change-Id: I41b2bf9fe3bc8df627c6650960bd11346c430a7e