Fix exceptions thrown in tests

Change-Id: Ia1327511d4347550111334fb858053a8cd8c3109
Conscrypt: correct key selection with no sigAlg

The KeyManagerImpl was changed to support the "EC_EC" and "EC_RSA" key
types in the StandardNames document. The intention of those aliases are
to require a certain signature type. If it is missing, it should accept
any signature type as before. However, it was erroneously requiring the
same signature type as the key type if it was missing. This causes RSA
client certificates signed by an EC key, for instance, to fail.

Bug: 10966884
Change-Id: I298bf65ac4c607ae13e24b44fb1b52ec341f9fcf