Set links up when probing interfaces during installation. See bnc#792985.

Setting interfaces up used to be side effect of NetHwDetection before.
However this side effect was removed when fixing bnc#782283.

The commit was cherry-picked from Code-11-SP3 branch and should be
placed before ab152d7, but was overlooked.

Conflicts:
	src/installation/inst_netprobe.ycp