rescue: error-proof 60-apt

It's not a blocker if enabling online repos fails;
we should provide a better handling of warnings
with e.g. a summary of those after build.

features.in/rescue/rescue/image-scripts.d/60-apt

@@ -1,4 +1,4 @@
 #!/bin/sh
 # enable online repository even more unconditionally
 
-sed -i "s,^#\(rpm \[alt\] http.*\),\1," "/etc/apt/sources.list.d/yandex.list"
+sed -i "s,^#\(rpm \[alt\] http.*\),\1," "/etc/apt/sources.list.d/yandex.list" ||	echo "** warning: unable to enable online repos" >&2