Changed the message line of RouterInUse class

Implements: Changed the message line of RouterInUse class,
so user will not get confused with active or inactive ports
while deleting the router.

Closes-Bug: #1236372
Change-Id: I7a82550e2c6051f9e4940a8f1dd4401059e0a8d8
Restore NOT NULL constraint lost by earlier migrations

Bring back nullable=False for columns in tables poolstatisticss
and ipsec_site_connections that disapeared because of
migrations abc88c33f74f and 338d7508968c correspondingly.

Closes-bug: #1288681

Change-Id: Idc4608616c2b4c06e7404157b2f708d46e91accc
Use os.uname() instead of calling uname in subprocess

Related-Bug: #1291535

Change-Id: I57e18c0b95904f318e3fff08cd18b32e28f48834
Remove invalid copyright headers under API module

Change-Id: I629b639f6c94654117fbafb8b21840f7ba6b045a
Partial-bug: #1262424
Merge "Use os.uname() instead of calling uname in subprocess"
Merge "Changed the message line of RouterInUse class"
Merge "Remove invalid copyright headers under API module"
Merge "Restore NOT NULL constraint lost by earlier migrations"