change api CreateOrUpdateMantleBackup to CreateMantleBackup #903

Job	Run time
build (3Mi, incr-backup)	35m 9s
build (3Mi, change-to-primary)	29m 11s
build (3Mi, full-backup)	28m 18s
build (200Gi, various-transfer-part-size)	20m 47s
build (3Mi, !//)	38m 41s
build (3Mi, change-to-secondary)	27m 51s
build (10Mi, various-transfer-part-size)	21m 22s
build (3Mi, backup-failure)	32m 27s
build (3Mi, change-to-standalone)	22m 35s
build (3Mi, lock)	21m 3s
	4h 37m 24s

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