MSTP update - 6: added bridge port initialization

Added #bridge #port #initialization #routine in MSTP module. On activating the spanning tree on a port it #set s #default #value s as in CIST root bridge, IST root bridge, CIST path cost, IST path cost, etc ... on it.

#802-1S #MSTP update 6 ...
[commit 0d76f089e5fe37da544fa35d23e640ac45efecf0]