cfm: Extracts the cfm status in one function.

cfm: Extracts the cfm status in one function.

This commit adds a new function, cfm_get_status(), for extracting
all cfm status at once.  This helps avoid the sequence of lock
acquire/release in current implementation of status query.

Signed-off-by: Alex Wang <alexw@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>