Adds conditional steps for reports

If coverage or junit files exist, publish them via Jenkins
plugins.

Junit plugin is already present.
Coberatura plugin needs to be installed before this can be
merged.

Bug 803

Change-Id: I898e32a6b9dd28c958e7fea2422c416f3c2c077e
Signed-off-by: beierl <mbeierl@vmware.com>