bridge fdb: add 'use' option to set NTF_USE flag in fdb add requests

bridge fdb: add 'use' option to set NTF_USE flag in fdb add requests

This is similar to command options corresponding to other NTF_* flags
already exposed to the user space (examples self/master).

Also updates bridge man page (The man page patch also includes
a fix to the 'self' entry and documents 'master' for fdb entries)

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Reviewed-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>