MXS-2170 Start MaxScale normally if it gets the same PID as previous

MaxScale

Check is made to see if the found MaxScale PID is owned by the process
itself.

server/core/gateway.cc

@@ -2368,7 +2368,7 @@ bool pid_is_maxscale(int pid)
 
     if (file && std::getline(file, line))
     {
-        if (line == "maxscale")
+        if (line == "maxscale" && pid != getpid())
         {
             rval = true;
         }