Don't count busy buffers before the initial call to sync() and
don't skip the initial sync() if no busy buffers were called.
Always call sync() at least once if syncing is requested. This
defers the "Syncing disks, buffers remaining..." message until
after the initial sync() call and the first count of busy
buffers. This backs out changes in kern_shutdown 1.162.
Print a different message when there are no busy buffers after the
initial sync(), which is now the expected situation.
Print an additional message when syncing has completed successfully
in the unusual situation where the work of syncing was done by
boot().
Uppercase one message to make it consistent with all of the other
kernel shutdown messages.
Discussed with: bde (in a much earlier form, prior to 1.162)
Reviewed by: njl (in an earlier form)
b6915bdbe5