CredManagerBackedSecureStore get method shoud treat secret bytes as UTF_16LE

[normanhuang]

vsts-authentication-library-for-java/storage/src/main/java/com/microsoft/alm/storage/windows/internal/CredManagerBackedSecureStore.java

Line 90 in edee296

final String secret = StringHelper.UTF8GetString(secretBytes);

In the current implementation, the secret bytes are incorrectly decoded as UTF8. As a result, the Password of the newly created Credential object does not match the original password.