Move QVk_Postinit() from render init to context init.

This is more in line with the rest of the code. Reinitializing the
internal state when building a new context is saver than relying on
Vulkan telling us that something is wrong an reacting to that.

src/client/refresh/vk/vk_rmain.c

@@ -1329,8 +1329,6 @@ static qboolean RE_Init( void )
 	// print device information during startup
 	Vk_Strings_f();
 
-	QVk_PostInit();
-
 	R_Printf(PRINT_ALL, "Successfully initialized Vulkan!\n");
 
 	return true;
@@ -1594,6 +1592,8 @@ RE_InitContext(void *win)
 		return false;
 	}
 
+	QVk_PostInit();
+
 	return true;
 }