Support password protected keystore

IMPALA-12380 allow user to store jdbc password in a Java keystore file on HDFS.
Keystores are generally password protected and so user need a password for accessing keystore. (See https://hadoop.apache.org/docs/stable/hadoop-project-dist/hadoop-common/CredentialProviderAPI.html#Keystore_Passwords).

From the Credential API link, if keystore has a password then it can be accessed if password is provided using either the environment variable "HADOOP_CREDSTORE_PASSWORD" or a file containing password and configured in core-site.xml with key hadoop.security.credstore.java-keystore-provider.password-file (See
https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/ProviderUtils.java#L214)