Netdata creates its control socket at /tmp/netdata-ipc by default, which
is insecure and actually inaccessible with systemd's PrivateTmp enabled.
Originally we patched its source code to move the socket to
/run/netdata/ipc. However, it was removed due to incompatibility when
upgrading to v1.41.0: 1d2a2dc7d0
Fortunately, this new version of netdata adds support for setting the
location of the control socket via the environment variable
NETDATA_PIPENAME. So let's set it for the netdata service and the
command line utility so that they can communicate properly.