client: add is_wrapper flag to APP_VERSION.  If set, the main program uses little CPU and can be run at elevated priority

VBOX: Adjust the VM process priority right before a suspend command to speed up how quickly the VM is suspended.

VBOX: Use the same technique for calculating when to report a trickle as we use for performing checkpoints.

Deleting previous checkpoints take progressively longer the longer the VM has been running.  The previous method just added 1 second of elapsed time to a variable instead of the real amount of wall clock time to the variable.

client: clear no_rsc_apps[] flags before parsing scheduler reply.  Otherwise they'll never get cleared if server doesn't explicitly send.