Change kenwood_set_mode to only change mode if necessary by reading it first

https://github.com/Hamlib/Hamlib/issues/726

rigs/kenwood/kenwood.c

@@ -2046,8 +2046,13 @@ int kenwood_set_mode(RIG *rig, vfo_t vfo, rmode_t mode, pbwidth_t width)
     }
     else
     {
-        snprintf(buf, sizeof(buf), "MD%c", c);
-        err = kenwood_transaction(rig, buf, NULL, 0);
+        pbwidth_t twidth;
+        err = rig_get_mode(rig, vfo, &priv->curr_mode, &twidth);
+        // only change mode if needed
+        if (priv->curr_mode != mode) {
+            snprintf(buf, sizeof(buf), "MD%c", c);
+            err = kenwood_transaction(rig, buf, NULL, 0);
+        }
     }
 
     if (err != RIG_OK) { RETURNFUNC(err); }

rigs/kenwood/kenwood.h

@@ -28,7 +28,7 @@
 #include "token.h"
 #include "misc.h"
 
-#define BACKEND_VER "20210427"
+#define BACKEND_VER "20210615"
 
 #define EOM_KEN ';'
 #define EOM_TH '\r'