sysrc.get: be more quiet

sysrc.get is frequently used by states like sysrc.absent, where it is
expected that the variable will not be present.  So don't write errors
to the log file.

salt/modules/sysrc.py

@@ -49,7 +49,7 @@ def get(**kwargs):
     else:
         cmd += " -a"
 
-    sysrcs = __salt__["cmd.run"](cmd)
+    sysrcs = __salt__["cmd.run"](cmd, output_loglevel="quiet")
     if "sysrc: unknown variable" in sysrcs:
         # raise CommandExecutionError(sysrcs)
         return None