Windows: Do not defer Synchronous operations

Windows: Do not defer Synchronous operations

There is nothing to be gained by posting a synchronous write.
Let it hang out in CcCopyWrite until there is enough memory
unless the write became synchronous after a deferral in which
case it can be deferred again.

Introduce bWait variable which is set to the result of
IoIsSynchronousWrite( Irp).

This change is being introduced after further analysis of the
FastFat example.

Change-Id: I0942975a142b0413e52076ee94977401c1d00dc9
Reviewed-on: http://gerrit.openafs.org/11067
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Rod Widdowson <rdw@steadingsoftware.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>