Circus Train should also sync the external schema for Avro Tables when replication mode is METADATA_UPDATE

[abhimanyugupta07]

As a user of CT,

I want that the Circus Train should also sync the external schema for an Avro Table when the replication mode is either METADATA_UPDATE or METADATA_MIRROR.

Context
At the moment, when the replication mode is METADATA_UPDATE or METADATA_MIRROR, the table location is not needed to be provided in the config file which means that the null check on https://github.com/HotelsDotCom/circus-train/blob/master/circus-train-avro/src/main/java/com/hotels/bdp/circustrain/avro/transformation/AbstractAvroSerDeTransformation.java#L50 returns empty and the Avro Transform is not triggered which in turn will not copy the schema file to replica.

This was discovered while working on: #131

Related PR: #141

Possible Solution
CT can detect if the table location is not provided and in the Avro transform, it can get the table location from the target HMS.

[patduin]

This is not needed for METADATA_MIRROR as that is an exact metadata copy of the table so all locations will be the same