libnfs.c: Fix autoreconnect

Since rpc_connect_async sets autoreconnect to 0, turn autoreconnect on
after the connection has completed, not before.

This fixes #76.

Signed-off-by: Ross Lagerwall <rosslagerwall@gmail.com>
Merge pull request #88 from rosslagerwall/76-no-autoreconnect

libnfs.c: Fix autoreconnect