[DOP-23122] Use async methods of Keycloak client #1445

Job	Run time
S3 tests / Run S3 tests	11m 3s
Hive tests / Run Hive tests	6m 58s
SFTP tests / Run SFTP tests	4m 3s
Samba tests / Run Samba tests	4m 51s
Scheduler tests / Run Scheduler tests	1m 29s
Clickhouse tests / Run Clickhouse tests	8m 24s
FTP tests / Run FTP tests	9m 36s
MSSQL tests / Run MSSQL tests	7m 38s
Unit tests / Run unit tests	3m 27s
WebDAV tests / Run WebDAV tests	8m 7s
FTPS tests / Run FTPS tests	4m 28s
Oracle tests / Run Oracle tests	8m 1s
MySQL tests / Run MySQL tests	4m 11s
HDFS tests / Run HDFS tests	7m 42s
Tests done	25s
	1h 30m 23s

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