Cyclon get_k_view should return a list of IPs

[robzenn92]

Right now get_k_view() route in cyclon/app.py returns a list of PodDescriptor. However, EpTO does not need to know what is a PodDescriptor, neither will use the concept of "age" for each peer. Hence, get_k_view() should return a list of IPs so that EpTO can simply go through the list and send messages to each entry of the list.