Add support key replicas mechanism for KMS HA

The patch HADOOP-11620 only supports specification of multiple hostnames in the kms key provider uri. it means that it support config as:

<property>
<name>hadoop.security.key.provider.path</name>
<value>kms://http@[HOSTNAME1];[HOSTNAME2]:16000/kms</value>
</property>

but HA is still not available, if one of KMS instances goes down, Encrypted files, which encrypted by the keys in the KMS, can not be read.