@Override
  protected void persistCredentialStore(KeyStore keyStore) throws AmbariException {
    throw new UnsupportedOperationException();
  }
Tests this CredentialStore for the existence of a credential with the specified alias
<p/>
This implementation is thread-safe, allowing one thread at a time to access the credential store.

@param alias a string declaring the alias (or name) of the credential
@return true if the alias exists; otherwise false
@throws AmbariException if an error occurs while searching forthe credential
ambari-server/src/main/java/org/apache/ambari/server/security/encryption/InMemoryCredentialStore.java