update: fix osd flickering

Origin commit data
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Commit: 6709cffc6e
Author: vanhofen <vanhofen@gmx.de>
Date: 2017-10-25 (Wed, 25 Oct 2017)

Origin message was:
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- update: fix osd flickering

src/gui/update.cpp

@@ -669,6 +669,12 @@ int CFlashUpdate::exec(CMenuTarget* parent, const std::string &actionKey)
 #ifndef DRYRUN
 		my_system(3, ofgwrite_tgz, g_settings.update_dir.c_str(), filename.c_str());
 #endif
+		/*
+		   ofgwrite is killing Neutrino.
+		   So we stay here and wait for our end. This avoids osd flickering.
+		*/
+		while (true)
+			sleep(1);
 	}
 #endif
 	else // not image, install