RouterInfo class has got internal_ports cache which is updated
in _process_internal_ports() method.
There was an issue in this updates logic because it was
iterating through enumerate local variable "internal_ports"
which represents current router ports and if such current port
was found in updated_ports list it was storred in
RouterInfo().internal_ports variable under same index as was
found in "internal_ports" local variable.
This sometimes leads to an issue because same port can be
stored under different index in internal_ports and
RouterInfo().internal_ports lists thus wrong port in
RouterInfo().internal_ports was overwritten.
Such issue leads to problem with generating radvd config file
because in ports cache list there was duplicate info about same port
so radvd config file contained duplicate interface definitions too.
This should be properly fixed by changing RouterInfo.internal_ports
to be a dict instead of list of ports but such patch would be much
bigger and (possibly) harded to backport to stable branches.
Change-Id: I2e38457942518c8a3e07e606091bb6720317b77e
Closes-Bug: #1813279
(cherry picked from commit 21cddc47b4)
10c981512a