main: Introduce defaultErrorFile
main: Introduce defaultErrorFile

Add a "defaultErrorFile" variable for parity with "defaultOutputFile"
and to allow testing the fatal() function (which now uses
defaultErrorFile).

Signed-off-by: James O. D. Hunt <348fbaadfbada55ea105602bf5609e23ac1c4898@intel.com>

clearcontainers/runtime,chavafg/runtime,devimc/runtime,devimc/runtime,chavafg/runtime,clearcontainers/runtime