packstack: find out which package provides 'nc'.

Only with 'rpm -q' we my fail to query 'nc' capability. This patch
corrects it.

Bug Url: https://bugzilla.redhat.com/show_bug.cgi?id=1018551

Change-Id: Iff6fc1129ba7ad05f253ab482aeb00c482402fcd
Signed-off-by: Humble Chirammal <hchiramm@redhat.com>