Do not restart the scan in vm_object_page_clean() on the object generation change if requested mode is async. The object generation is only changed when the object is marked as OBJ_MIGHTBEDIRTY. For async mode it is enough to write each dirty page, not to make a guarantee that all pages are cleared after the vm_object_page_clean() returned.
Do not restart the scan in vm_object_page_clean() on the object
generation change if requested mode is async. The object generation is
only changed when the object is marked as OBJ_MIGHTBEDIRTY. For async
mode it is enough to write each dirty page, not to make a guarantee that
all pages are cleared after the vm_object_page_clean() returned.

Diagnosed by:	truckman
Tested by:	flo
Reviewed by:	alc, truckman
MFC after:	2 weeks

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase