This adds support for reading sec= option and sending security data
through cache via "... secinfo n flavor1 flag1 ... flavorN flagN".
If sec= is missing, no secinfo option will be passed down.
Signed-off-by: Fred Isaman <iisaman@citi.umich.edu> Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu> Signed-off-by: Neil Brown <neilb@suse.de>