The FUSE harness picks the filer HTTP port and lets "weed mount" derive the
filer gRPC port as HTTP+10000. freePort kept the HTTP port under the Linux
ephemeral floor (32768) but not the derived gRPC port, which ranged up to
42000. When the gRPC port landed above the floor an outbound connection could
transiently hold it, so mini relocated its filer gRPC port while mount kept
dialing HTTP+10000, timing the mount out.
Cap the HTTP port at 22000 so the gRPC sibling stays at or below 32000, and
verify both ports are bindable before returning.
Chris Lu
68e6fc5f7c