fix(client): detect valid eof after reading a body
fix(client): detect valid eof after reading a body

If a connection closes immediately after reading the end of the body,
the next call to `conn.poll()` should not error, but just indicate
that the connection is done.

Closes #1396

tshepang/hyper,hyperium/hyper,hyperium/hyper,hyperium/hyper,tshepang/hyper,yazaddaruvala/hyper,yazaddaruvala/hyper,tshepang/hyper