HORNETQ-1429 Fixing proton session.close and connection.close leaking connections

This is a small fix after the main refactoring.
Session.close() was leaving sessions around what was making the connection.close() to
ignore close calls and leak connections
Merge pull request #1927 from clebertsuconic/master

HORNETQ-1429 Fixing proton session.close and connection.close leaking connections