lisa.tests.scheduler.load_tracking: Make CPUMigrationBase.test_util_migration more robust
lisa.tests.scheduler.load_tracking: Make CPUMigrationBase.test_util_migration more robust

Correct the expected utilization according to the rt-app calibration values.
This allows rt-app calibration to not match precisely the CPU capacities.

ARM-software/lisa,credp/lisa,credp/lisa,ARM-software/lisa,credp/lisa,credp/lisa,ARM-software/lisa,ARM-software/lisa