Update pgo-apiserver for newer buildah versions

Must add ARG for PGVERSION after the FROM or it doesn't
get set with newer buildah versions.

Author: crunchyheath

build/pgo-apiserver/Dockerfile

@@ -7,6 +7,7 @@ FROM ${PREFIX}/pgo-base:${BASEOS}-${BASEVER}
 
 ARG BASEOS
 ARG PACKAGER
+ARG PGVERSION
 
 LABEL name="pgo-apiserver" \
 	summary="Crunchy PostgreSQL Operator - Apiserver" \