Test tor dormant mode

Working on legacy/trac#30733 (moved) asn pointed out to check the dormant mode. Dormant mode was introduced in tor 0.4.0.4-rc.

As teor suggested, we should check whether sbws stop trying to make circuits, and therefore become dormant, when:

• the network goes down (it probably just stops and prints a traceback, as happened in legacy/trac#32939 (moved))
• tor doesn't have a recent consensus or descriptors

We also should check what happen when sbws starts with tor in dormant mode and probably set DormantCanceledByStartup 1 until we fix bugs.

Maybe we should include this ticket as part of legacy/trac#33121 (moved).