Merged two run commands into one in Dockerfile

weaveexec/Dockerfile

@@ -1,9 +1,20 @@
 FROM gliderlabs/alpine
+
 MAINTAINER Weaveworks Inc <help@weave.works>
+
+RUN apk add --update \
+    curl \
+    ethtool \
+    iptables \
+    iproute2 \
+    util-linux \
+    conntrack-tools \
+  && rm -rf /var/cache/apk/*
+
 WORKDIR /home/weave
-RUN ["apk", "add", "--update", "ethtool", "conntrack-tools", "curl", "iptables", "iproute2", "util-linux"]
-RUN ["sh", "-c", "rm -rf /var/cache/apk/*"]
+
 ADD ./weave /home/weave/
 ADD ./sigproxy /home/weave/
 ADD ./docker.tgz /
+
 ENTRYPOINT ["/home/weave/sigproxy", "/home/weave/weave"]