client: merge (re)init code and introduce context_alloc()

The init and reinit code does nearly the same.
client: reinitialize all brokers when main loop starts
client: removed standby argument from alloc

context_alloc(.., standby) was only used with 1.
ctx->standby_only = 1 is set within context_reinitialize()
client: cancel running async jobs when context is reinitialized
client: remove duplicated broker reset - now done in reinitialize
client: set bandwidth settings within context_alloc
client: set ctx->state to a safe state when reinit fails
client: make sure a resolver is running in state RESOLVING
client: reset all brokers when the connection is lost
client: append package type to syslog messages
client: fix crash and memory leak with broker_resq
client: report bind() failure to syslog