Add image upload log directory and arguments. This is where provider
upload logs configured in Ic80e532891f039e0f835847ddfbae38f1ce3cd8aIf
can be stored.
Note http export (which we do not enable in infra at this time) would
put logs under /upload ; it might be more logical to move the build
logs to be a sibling at /build but that would be backwards
incompatbile.
Change-Id: I0cc9b59063fb14920f0da581b8036c2664d5d5f1
cd086492a4