Fixed Locking issue for VXLAN port and Slice ID gen

not releasing storage lock to switch event manager to update the vxlan
port details in topo DB - that's why time out occurred to slice manager
while waiting for vxlan port in topoDB

Slice name generation from vxlan port name: vxlan2526 whould be: 2526.
Where it is generated as n252

Added YaonUtil provide yaon's utility.