[NTOS]: Fix premature setting of the page location of a newly allocated MDL page...

[NTOS]: Fix premature setting of the page location of a newly allocated MDL page. Because the zeroing of non-zeroed pages is done after the initial page allocation loop (and by checking which list the page was on), setting the page location as ActiveAndValid made the zero loop believe the page was unzeroed (even though it could've come from the zeroed list), causing a superflous second zero operation.

svn path=/trunk/; revision=45625