Print the full command, this allows the grep to find a match when
a proxy minion is running. Otherwise it incorrectly determine the
given proxy isn't running and fork off another copy repeatedly.

Index: salt/modules/salt_proxy.py
--- salt/modules/salt_proxy.py.orig
+++ salt/modules/salt_proxy.py
@@ -71,7 +71,7 @@ def _is_proxy_running(proxyname):
     """
     Check if proxy for this name is running
     """
-    cmd = 'ps ax | grep "salt-proxy --proxyid={}" | grep -v grep'.format(
+    cmd = 'ps axww | grep "salt-proxy --proxyid={}" | grep -v grep'.format(
         shlex.quote(proxyname)
     )
     cmdout = __salt__["cmd.run_all"](cmd, timeout=5, python_shell=True)