Define the available data plane vlan range(s) in the manifest

[YufengXin]

Currently, they start from 1 and so on. We may not have that flexibility and need some VLAN ranges for dataplane connections.
That was one underimplemented function we noted in the audit report because the range [1,4089] is hard coded in two functions in sdxctrl/TopologyManager.py:

def find_vlan_on_tree(self, tree):

def find_vlan_on_path(self, path):

as part of finding the valid path and tree in the data plane.

Need to define the available range(s) in the manifest. But for the time being, probably just change the hard code.

[YufengXin]

Manifest allows to define individual clan ranges per link.

Added a new function to find disjoint vlan per link along a path: TopologyManager.py
def find_vlans_on_path(self, path):

Need more tests on vlan reservation per link along a path:
first, on the L2TunnelPolicy