After the new libcontainer API, the reexec.Self() output of the daemon
binary is used as the libcontainer factory InitPath. If it is relative,
it can't be found at container start time. This patch solves the
problem by making sure that we return a rooted/absolute path if a
relative path is used.
Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)
