evs_app : Call detachRenderTarget to free resources

* Call detachRenderTarget after drawFrame to free resources

* If detachRenderTarget isn't called, drawFrame return false and evs_app restart.
  Cause of restart evs_app, the display blink.
diff --git a/evs/app/RenderDirectView.cpp b/evs/app/RenderDirectView.cpp
index 24eb485..45dfa78 100644
--- a/evs/app/RenderDirectView.cpp
+++ b/evs/app/RenderDirectView.cpp
@@ -135,6 +135,6 @@
 
     // Wait for the rendering to finish
     glFinish();
-
+    detachRenderTarget();
     return true;
 }
diff --git a/evs/app/RenderTopView.cpp b/evs/app/RenderTopView.cpp
index 1579a0a..e8f7399 100644
--- a/evs/app/RenderTopView.cpp
+++ b/evs/app/RenderTopView.cpp
@@ -214,7 +214,7 @@
 
     // Wait for the rendering to finish
     glFinish();
-
+    detachRenderTarget();
     return true;
 }