clear boot-animation background with black (not transparent) pixels

Change-Id: I2fcf9f303e8324cefaa2d96f1c46647f70980bb2
diff --git a/cmds/bootanimation/BootAnimation.cpp b/cmds/bootanimation/BootAnimation.cpp
index f987d61..69c4597 100644
--- a/cmds/bootanimation/BootAnimation.cpp
+++ b/cmds/bootanimation/BootAnimation.cpp
@@ -302,6 +302,7 @@
     glShadeModel(GL_FLAT);
     glDisable(GL_DITHER);
     glDisable(GL_SCISSOR_TEST);
+    glClearColor(0,0,0,1);
     glClear(GL_COLOR_BUFFER_BIT);
     eglSwapBuffers(mDisplay, mSurface);
 
@@ -439,6 +440,7 @@
     glDisable(GL_DITHER);
     glDisable(GL_SCISSOR_TEST);
     glDisable(GL_BLEND);
+    glClearColor(0,0,0,1);
     glClear(GL_COLOR_BUFFER_BIT);
 
     eglSwapBuffers(mDisplay, mSurface);