exportfs -r without -B fails because it skips the initial protocol.

For example, executing this one on host A
% aux/listen1 -tv tcp!$addr!64470 /bin/exportfs -r /dev
and executing this on host B
% import -A tcp!$addr!64470 
will typically either fail to read the initial string or result in a bad tree.

I believe that exportfs should only skip the initial protocol with -B, -S, etc.
The fix entails reading the path requested by import and discarding it.