Handle path prefix in Elasticsearch url

Context

Indexer and Search connection to Elasticsearch fails if the ElasticSearch Url contains a path after host. This is the value specified in the "ELASTIC_HOST" environment variable for the ITs, and "elastic-username" value from partition info for the Services. There is no provision to specify the path.

Example: host.com works but host.com/elasticsearch leads to failure.

Problem

There has been an update in Azure elasticsearch endpoint. Earlier it did not have a path, now it does. Due to this Azure ITs are failing on master branch.

Proposed Solution

For IT's, build the rest client by taking the path along with host, port and scheme into account. For Services, we can revisit the way of specifying the URL. Instead of having ELASTIC_HOST, ELASTIC_SSL_ENABLED, ELASTIC_PORT, we can let the user specify ELASTIC_URL instead, in one shot.