host: Cleanup containers concurrently

Signed-off-by: Lewis Marshall <lewis@lmars.net>
script: Give the host more time to cleanup jobs

Signed-off-by: Lewis Marshall <lewis@lmars.net>
script: Use unique log file when bootstrapping

Signed-off-by: Lewis Marshall <lewis@lmars.net>
script: Symlink /tmp/flynn-host.log to latest log

Signed-off-by: Lewis Marshall <lewis@lmars.net>
host: Don't remove the state file on exit

Signed-off-by: Lewis Marshall <lewis@lmars.net>
host: Ignore existing symlinks when watching containers

Closes #143

Signed-off-by: Lewis Marshall <lewis@lmars.net>
script: Use a state file when bootstrapping

Signed-off-by: Lewis Marshall <lewis@lmars.net>
script: Support bootstrapping docker backend

Signed-off-by: Lewis Marshall <lewis@lmars.net>