Increased the number of threads in RestDeviceProvider to avoid timeouts

Change-Id: I6ab4b1d0eb655b32f7816abfd11c3dfee296d9b1
diff --git a/providers/rest/device/src/main/java/org/onosproject/provider/rest/device/impl/RestDeviceProvider.java b/providers/rest/device/src/main/java/org/onosproject/provider/rest/device/impl/RestDeviceProvider.java
index 61d1625..a8d0655 100644
--- a/providers/rest/device/src/main/java/org/onosproject/provider/rest/device/impl/RestDeviceProvider.java
+++ b/providers/rest/device/src/main/java/org/onosproject/provider/rest/device/impl/RestDeviceProvider.java
@@ -102,6 +102,7 @@
     private static final String UNKNOWN = "unknown";
     private static final int REST_TIMEOUT_SEC = 5;
     private static final int DEFAULT_POLL_FREQUENCY_SECONDS = 30;
+    private static final int EXECUTOR_THREAD_POOL_SIZE = 8;
     private final Logger log = getLogger(getClass());
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
@@ -158,7 +159,9 @@
         appId = coreService.registerApplication(APP_NAME);
         providerService = providerRegistry.register(this);
         factories.forEach(cfgService::registerConfigFactory);
-        executor = Executors.newFixedThreadPool(5, groupedThreads("onos/restsbprovider", "device-installer-%d", log));
+        executor = Executors.newFixedThreadPool(
+            EXECUTOR_THREAD_POOL_SIZE, groupedThreads("onos/restsbprovider", "device-installer-%d", log)
+        );
         cfgService.addListener(configListener);
         executor.execute(RestDeviceProvider.this::createAndConnectDevices);
         executor.execute(RestDeviceProvider.this::createDevices);