Uneeded create collection operation for the not-capped case

[fgalan]

We have

fiware-cygnus/cygnus-common/src/main/java/com/telefonica/iot/cygnus/backends/mongo/MongoBackendImpl.java

Lines 94 to 123 in d7a962a

	@Override
	public void createCollection(String dbName, String collectionName, long dataExpiration) throws MongoException {
	LOGGER.debug("Creating Mongo collection=" + collectionName + " at database=" + dbName);
	MongoDatabase db = getDatabase(dbName);
	// create the collection
	try {
	db.createCollection(collectionName);
	} catch (MongoException e) {
	ErrorCategory errorCategory = ErrorCategory.fromErrorCode( e.getCode() );
	if (errorCategory == ErrorCategory.fromErrorCode(48)){
	LOGGER.debug("Collection already exists, nothing to create");
	} else {
	throw e;
	} // if else
	} // try catch
	// check STH indexes documentation at https://github.com/telefonicaid/fiware-sth-comet/blob/master/doc/manuals/db_indexes.md
	BasicDBObject keys;
	IndexOptions options;
	try {
	keys = new BasicDBObject()
	.append("_id.entityId", 1)
	.append("_id.entityType", 1)
	.append("_id.attrName", 1)
	.append("_id.resolution", 1)
	.append("_id.origin", 1);
	options = new IndexOptions().name("cyg_agg_opt");
	db.getCollection(collectionName).createIndex(keys, options);
	} catch (Exception e) {

The "create the collection block" (L99-L109) is not needed, as the createIndex() operation in L122 will automatically create the collection in this case.

(Explicit create collection is needed for capped collections, which are dealt in the other createCollection() method we have in that class)

[fgalan]

Fixed in PR #2164