pkg-export-docker: Don't duplicate option aliases
pkg-export-docker: Don't duplicate option aliases

This patch fixes the regression from
110936abd800e2e27c62200144ae56b3af0d9a90 where '-P' option aliases were
added multiple times.

Signed-off-by: Zeeshan Ali <1298e36e813af35ccce9deecc1a60eb678eb9692@gmail.com>

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