Flaky keychain test

[Benehiko]

The keychain package has a flaky test: TestKeychain/list_all_credentials

#17 9.770 === RUN   TestKeychain
#17 9.770 === RUN   TestKeychain/save_credentials
#17 9.770 === RUN   TestKeychain/get_credential
#17 9.770 === RUN   TestKeychain/list_all_credentials
#17 9.770     keychain_test.go:133: 
#17 9.770         	Error Trace:	/app/store/keychain/keychain_test.go:133
#17 9.770         	Error:      	Received unexpected error:
#17 9.770         	            	failed to create item: Couldn't create item: The secret was transferred or encrypted in an invalid way.
#17 9.770         	Test:       	TestKeychain/list_all_credentials