RFC: Check local status before connecting to remote branch.

[Raindog]

I think it would be best if bzr would perform a local verification prior 
to connecting to a remote server to determine whether or not the 
operation would succeed based upon the condition of the local branch.

For example, if my local branch is in a conflicted state, and I try to 
update from the remote branch, bzr should make the failure check before 
it tries to connect because it can know before hand that the operation 
will fail.