pg_restore dependencies

We still have a little work to do on dependencies in parallel 
pg_restore. The current test compares the candidate's locking 
dependencies with those of the running jobs, and allows the candidate is 
there isn't a match. That's not a broad enough test. The candidate will 
block if there's a currently running CREATE INDEX command on the table, 
for example, even though that doesn't require an exclusive lock. That's 
not catastrophic, in that the restore doesn't fail, but it's fairly bad 
because it reduces the achievable parallelism. Josh Berkus observed this 
during testing on a very large restore.

cheers

andrew