Two semi-related exports_setup changes.
1. Don't stat all exported mountpoints from boss to see if they exist. Not only is this wrong from boss (a mount may be valid, but not yet exported) it also makes the automounter work its butt off as we might stat hundreds or thousands of directories across NFS. The original purpose of this was to keep mountd from freaking out when presented with a non-existent directory. Since mountd freaking out is about as rare as the sun rising in the east, we keep this check but do it on the proxy (ops) side instead. 2. Have exports_setup (boss) generate a list of directories that it should be able to mount. This goes in /usr/testbed/etc/validmounts.txt and will be used by autofs (I hope) to narrow down the wildcarded "/users/*" and "/proj/*" mounts to those that might actually work. Right now you can "ls /users/WtF" and it will try to mount it from ops and take 4 seconds to timeout and fail.