Using no-cache while upgrading for consistency

Author: Angatar

Dockerfile

@@ -3,7 +3,7 @@ LABEL org.opencontainers.image.authors="d3fk"
 LABEL org.opencontainers.image.source="https://github.com/Angatar/mysql-s3-backup.git"
 LABEL org.opencontainers.image.url="https://github.com/Angatar/mysql-s3-backup"
 
-RUN apk upgrade \
+RUN apk upgrade --no-cache \
   && apk add --no-cache mysql-client python3 py3-six py3-pip py3-setuptools libmagic git ca-certificates \
   && git clone https://github.com/s3tools/s3cmd.git /tmp/s3cmd \
   && cd /tmp/s3cmd \