support/linux/helpers: rm unnecessary dir check
support/linux/helpers: rm unnecessary dir check

`load_package` is helpful w/o `/src/pkgs`, don't expect the directory to
exist.

Signed-off-by: Michael Schubert <17b9e1c64588c7fa6419b4d29dc1f4426279ba01@kinvolk.io>

georgemarshall/habitat,georgemarshall/habitat,georgemarshall/habitat,nathenharvey/habitat,nathenharvey/habitat,rsertelon/habitat,habitat-sh/habitat,rsertelon/habitat,rsertelon/habitat,georgemarshall/habitat,nathenharvey/habitat,nathenharvey/habitat,nathenharvey/habitat,habitat-sh/habitat,georgemarshall/habitat,georgemarshall/habitat,habitat-sh/habitat,rsertelon/habitat,rsertelon/habitat,georgemarshall/habitat,rsertelon/habitat,georgemarshall/habitat,nathenharvey/habitat,habitat-sh/habitat,habitat-sh/habitat,rsertelon/habitat,habitat-sh/habitat,habitat-sh/habitat,habitat-sh/habitat