[DOP-23122] Use async methods of Keycloak client #1006

Job	Run time
HDFS tests / Run HDFS tests	8m 31s
Clickhouse tests / Run Clickhouse tests	4m 20s
Hive tests / Run Hive tests	5m 17s
Oracle tests / Run Oracle tests	4m 46s
MSSQL tests / Run MSSQL tests	4m 25s
MySQL tests / Run MySQL tests	4m 21s
S3 tests / Run S3 tests	8m 46s
Scheduler tests / Run Scheduler tests	3m 44s
Unit tests / Run unit tests	28m 19s
Tests done	1s
	1h 12m 30s

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