Decrease the initialization FSM timeout.

Decrease the initialization FSM timeout.

The previous value of 180 was just too long. If a neighbor get stuck in
the initialization FSM for more than 15 seconds, then there's certainly
something wrong and the session should be dropped.

A potential case of a neighbor getting stuck in the initialization
FSM is when both the local and the remote LSRs disable the LDPv4 GTSM
negotiation and there's a mismatch in their GTSM configuration (one is
enabled for GTSM while the other is not).

In this case, a smaller timeout allows for a quicker recovery of the
session when the configuration is fixed on either side.