fix LegacyKeyValueFormat warnings

> LegacyKeyValueFormat: "LABEL key=value" should be used instead of legacy "LABEL key value"
> LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value"

Author: linuxmaniac

create_dockerfile.sh

@@ -6,13 +6,13 @@ create_dockerfile() {
   cp -r "src/pkg/kamailio/deb/${dist}/" "${dist}/debian/"
   cat >"${dist}"/Dockerfile <<EOF
 FROM ${docker_tag}
-LABEL org.opencontainers.image.authors Victor Seva <linuxmaniac@torreviejawireless.org>
+LABEL org.opencontainers.image.authors="Victor Seva <linuxmaniac@torreviejawireless.org>"
 
 # Important! Update this no-op ENV variable when this Dockerfile
 # is updated with the current date. It will force refresh of all
 # of the base images and things like 'apt-get update' won't be using
 # old cached versions when the Dockerfile is built.
-ENV REFRESHED_AT ${DATE}
+ENV REFRESHED_AT="${DATE}"
 
 EOF