[LU-4604] improve LFSCK async RPCs control

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.6.0, Lustre 2.5.4
• Severity: 3
• Assignee: nasf (Inactive)
• Reporter: nasf (Inactive)

Description

Currently, the LFSCK registers commit callback to OSP, which will update the LFSCK async requests windows size and wakeup related threads. From the whole MDT stack view, such mechanism is not clean, if possible, we should hide the async RPC control inside OSP or low layer.