framework: add blacklist disconnect cause

Constant to be used when marking a Call as blacklisted.

Change-Id: If8e0ba7a2fb9b3ebbcfde04df48cd0ab14bba864
Signed-off-by: Roman Birg <roman@cyngn.com>
(cherry picked from commit aa7e2898ff7266171a8212e50b33f0cb77ae8fdf)