Set a default timeout on account add operation

ATM tests sometimes fails with "AssertionError: Timed out" after 30
minutes, which is clearly too much and causes logcat to cycle.

Bug: 396804492
Test: atest CtsDevicePolicyTestCases:android.devicepolicy.cts.AccountManagementTest
Flag: EXEMPT test change
Change-Id: Ib97ab572c54e126d4245b0b06179ecabf95f5cf1