[dist] Directly untar archive to destination

We are using all these files anyway. So there is no need to store them
temporarily in another directory.

Dockerfile.backend

@@ -3,12 +3,7 @@ FROM openbuildservice/base
 RUN /root/bin/docker-bootstrap.sh backend
 
 # Add our sign configuration
-ADD dist/obs-signd-conf.tar.bz2 sign
-RUN rm -rf /root/.gnupg; \
-    mv -v /sign/root/.gnupg /root/.gnupg; \
-    mv -v /sign/root/.phrases /root/.phrases; \
-    mv -v /sign/etc/ourkeyfile.asc /sign/etc/sign.conf /etc/; \
-    mv -v /sign/etc/sysconfig/signd /etc/sysconfig/signd
+ADD dist/obs-signd-conf.tar.bz2 /
 
 # Run our command
 WORKDIR /obs