Fix CDMA Roaming drawables

The current AOSP drawables are black, hence they are invisible.
That was fixed in the commit linked below already, but they look
strange.

http://bit.ly/e3vh1G

Changed to the HDPI icon to the standard Gingerbread grey
and then recreated the MDPI drawable from that, with some manual
touches since it looked better.

Change-Id: Ib2836f7baa427508a142bfe454f7a8c342852f64