Fixes #128: Fix early return when exception ratio is 100%

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/degrade/DegradeRule.java

@@ -153,7 +153,6 @@ public class DegradeRule extends AbstractRule {
 
     @Override
     public boolean passCheck(Context context, DefaultNode node, int acquireCount, Object... args) {
-
         if (cut) {
             return false;
         }
@@ -184,8 +183,8 @@ public class DegradeRule extends AbstractRule {
             }
 
             double realSuccess = success - exception;
-            if (realSuccess <= 0) {
-                return exception < RT_MAX_EXCEED_N;
+            if (realSuccess <= 0 && exception < RT_MAX_EXCEED_N) {
+                return true;
             }
 
             if (exception / success < count) {