Fix race between `OnDemandHousekeeping` and `housekeepingTick`
Fix race between `OnDemandHousekeeping` and `housekeepingTick`

This fixes the data race between the functions which could be running
in different goroutines.

Signed-off-by: Pradyumna Agrawal <03cedce92266521b27ead0d5753a433645ed42a4@vmware.com>

linux-on-ibm-z/cadvisor,linux-on-ibm-z/cadvisor,linux-on-ibm-z/cadvisor