ForwardingRulesManager allows provisioning of conflicting/duplicate flows

As discussed on the forum with Alessandro et al, this is to track the issue with the ForwardingRulesManager during installFlowEntry.

In the method addEntry(FlowEntry), the set of container merged flows, stored in toInstallList, is subject to conflict detection & duplicate check resulting in the non-conflicting flows stored in the list toInstallSafe.

However, in the end when the actual addEntriesInternal is called, the toInstallList is used in stead of the toInstallSafe. This needs to be fixed to use the toInstallSafe.

Without this the duplicate detection will not work.