Dont retry failed bigger amounts in migrate

src/cc/dapps/zmigrate.c

@@ -932,7 +932,7 @@ again:
         if ( (amount= find_sprout_amount(coinstr,zcaddr)) > txfee )
         {
             // generate taddr, send max of 10000.0001
-            static int64_t lastamount,lastamount2,lastamount3,lastamount4;
+            static int64_t lastamount,lastamount2,lastamount3,lastamount4,refamount = 500 * SATOSHIDEN;
             stdamount = 500 * SATOSHIDEN;
             if ( amount == lastamount && amount == lastamount2 )
             {
@@ -940,6 +940,10 @@ again:
                 if ( amount == lastamount3 && amount == lastamount4 )
                     stdamount /= 5;
             }
+            if ( stdamount < refamount )
+                refamount = stdamount;
+            else if ( refamount > stdamount )
+                stdamount = refamount;
             lastamount4 = lastamount3;
             lastamount3 = lastamount2;
             lastamount2 = lastamount;