Test place_connection() more

[sajith]

Resolves #102. Changes:

• Use a single TEManager instance throughout the app, thus avoiding TopologyManager invocations. The latter probably should be a hidden implementation detail of PCE; we should tackle that separately.
• Test place_connection() under various conditions.
• Remove some unused methods from connection controller.

Getting this merged is a pre-condition for getting to #225 (handling connection deletions). This is probably incomplete and there are likely to be issues, but we can test address them later once things are in place.

[coveralls]

Pull Request Test Coverage Report for Build 8299597160

Details

• 23 of 32 (71.88%) changed or added relevant lines in 6 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+12.1%) to 50.772%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
sdx_controller/messaging/rpc_queue_consumer.py	4	5	80.0%
sdx_controller/controllers/topology_controller.py	1	3	33.33%
sdx_controller/handlers/connection_handler.py	9	12	75.0%
sdx_controller/handlers/lc_message_handler.py	2	5	40.0%

Totals
Change from base Build 8287985217:	12.1%
Covered Lines:	699
Relevant Lines:	1409

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💛 - Coveralls