Fix KeyDeletionTest.DeleteAllKeys

Test failed to set default key validity, which caused keygen to fail.
Wasn't noticed because this test is typically disarmed.

Note:  This test will destroy all user data on the device (which is
why it is typically disarmed).

Bug: 187105270
Test: VtsAidlKeyMintTargetTest --arm_deleteAllKeys
Change-Id: I67e317fdfca15c95c6420918948d1416e97de482
Merged-In: I67e317fdfca15c95c6420918948d1416e97de482