Doc nova tempdir flag

fixes bug 1106394

tempdir is a new option in grizzly, as documented

patch2 makes explicit that the default value is none

Change-Id: Ia528b622b4783e01eb1a55e5e897ee00a90e7bd7
Removes link to booktype as that book is migrated to our toolchain.

Change-Id: Ie99b50ef571808239c7adeab32644607cf81c101
Merge "Doc nova tempdir flag"