Since commit c91c365, when starting the docker daemon without an
existing /var/lib/docker directory, it fails with:
2013/12/18 23:39:36 Unable to canonicalize root (%!s(*string=0xc210077c80)): lstat /var/lib/docker: no such file or directory
Move the symlink checking code to engine.New after the root dir has been
created.
Upstream-commit: 94821a33534a25fe906f3f66e1c06b1f2c877aac
Component: engine