spec: libwsman3 obsoletes libwsman1

While this make parallel installations impossible, it fixes issue #71
diff --git a/package/openwsman.spec.in b/package/openwsman.spec.in
index 35285e8..07ac9e1 100644
--- a/package/openwsman.spec.in
+++ b/package/openwsman.spec.in
@@ -150,6 +150,7 @@
 Summary:        Opensource Implementation of WS-Management
 Group:          System/Management
 Provides:       openwsman = %{version}
+Obsoletes:      libwsman1 < %{version}
 Obsoletes:      openwsman < %{version}
 
 %description -n libwsman3