KeyChain: Fix certificate dialog needs twice Cancel to disappear.

The reason is that it returns to onResume() when
keyChainAliasResponse!= null in finish() of KeyChainActivity.
Then it will start Activity of CredentialStorage again as well as
the certificate dialog appears. So it needs twice "Cancel" button
to disappear.

The change is deleting return for finish() in KeyChainActivity.

CRs-Fixed: 619722

Change-Id: Ib38741294e71b8be21d3cdff18e1c10d3cc91f4b