Bug 1244: Fixed BasePCEPSessionProposalFactory

-keepalive is set to Open Message, if it's value is configured to zero
-if keepalive is 0, deadtimer should also be set to 0

Change-Id: Ib1ae89d8b0726b91cbd33d483c5fb6373f787d64
Signed-off-by: Milos Fabian <milfabia@cisco.com>