IceTransport::isXXX() API are not thread-safe, not clear in which
state the transport is and not easy to manipulate (order of state).

This patch tries to solve that by:
- Procted API by a mutex
- Remove uneeded isComplete() API
- Ensure that each API are ordered (one at true implies true
  on all lower states: INITIALIZED -> STARTED -> RUNNING).
  All return false on Fail state.
- Change usage accordingly

Tuleap: #107
Change-Id: I17211e54322d70bbfe18c28f06cf9967b9ef93d2