ssdb-server 1.9.7 (#699)

* ssdb-server 1.9.7

On this version the server return 0 or 1

* ssdb-server 1.9.7 

In version 1.9.7 of ssdb, it replies with an integer instead of a Bolean generating the following error:
"Return value of Phpfastcache Drivers SSdb Driver :: driverDelete () must be of the type boolean, integer returned"
and
"Return value of Phpfastcache Drivers SSdb Driver :: driverClear () must be of the type boolean, integer returned"

Author: dmz86

lib/Phpfastcache/Drivers/Ssdb/Driver.php

@@ -100,7 +100,7 @@ protected function driverWrite(CacheItemInterface $item): bool
          * Check for Cross-Driver type confusion
          */
         if ($item instanceof Item) {
-            return $this->instance->setx($item->getEncodedKey(), $this->encode($this->driverPreWrap($item)), $item->getTtl());
+            return (bool) $this->instance->setx($item->getEncodedKey(), $this->encode($this->driverPreWrap($item)), $item->getTtl());
         }
 
         throw new PhpfastcacheInvalidArgumentException('Cross-Driver type confusion detected');
@@ -117,7 +117,7 @@ protected function driverDelete(CacheItemInterface $item): bool
          * Check for Cross-Driver type confusion
          */
         if ($item instanceof Item) {
-            return $this->instance->del($item->getEncodedKey());
+            return (bool) $this->instance->del($item->getEncodedKey());
         }
 
         throw new PhpfastcacheInvalidArgumentException('Cross-Driver type confusion detected');
@@ -128,7 +128,7 @@ protected function driverDelete(CacheItemInterface $item): bool
      */
     protected function driverClear(): bool
     {
-        return $this->instance->flushdb('kv');
+        return (bool) $this->instance->flushdb('kv');
     }
 
     /********************
@@ -156,4 +156,4 @@ public function getStats(): DriverStatistic
 
         return $stat;
     }
-}
+}