RFR 8197930: JNI exception pending in initializeEncoding of jni_util.c

[Roger Riggs]

Please review a cleanup to not ignore errors from GetMethodID and GetFieldID
while initializing the system encoding.

Webrev:
    http://cr.openjdk.java.net/~rriggs/webrev-jnicheck-8197930/
issue:
    https://bugs.openjdk.java.net/browse/JDK-8197930

Thanks, Roger