Fix get_powerstat in kenwood.c to reset err to RIG_OK

https://github.com/Hamlib/Hamlib/issues/242

rigs/kenwood/kenwood.c

@@ -717,6 +717,7 @@ int kenwood_open(RIG *rig)
             rig_debug(RIG_DEBUG_TRACE, "%s: got PS0 so powerup\n", __func__);
             rig_set_powerstat(rig, 1);
         }
+        err = RIG_OK;  // reset our err back to OK for later checks
     }
 
     if (err == -RIG_ETIMEOUT)

rigs/kenwood/kenwood.h

@@ -27,7 +27,7 @@
 #include <string.h>
 #include "token.h"
 
-#define BACKEND_VER "20200501"
+#define BACKEND_VER "20200508"
 
 #define EOM_KEN ';'
 #define EOM_TH '\r'