implicit assumption in keymanagerfactory: keys are protected with same password

The KeyManagerFactory API right now has room for one password, therefore
if there are any keys in a keystore which are protected by a different password,
we throw:

java.security.UnrecoverableKeyException: Cannot recover key
at sun.security.provider.KeyProtector.recover(KeyProtector.java:304)
at ...

The workaround is to have all entries protected by the same key, but
this may not be approrpriate in all situations. Either the API should
change, or this should be documented.

Brad