better logging in _handle_slots #659

Job	Run time
behave (archive)	4m 23s
behave (async)	6m 37s
behave (autofailover)	16m 5s
behave (cascade)	21m 19s
behave (consecutive_switch)	9m 37s
behave (coordinator)	10m 36s
behave (coordinator_fail)	15m 47s
behave (dead_primary_switchover)	15m 29s
behave (disable_sync)	9m 19s
behave (failed_promote)	29m 38s
behave (failover_timeout)	39m 1s
behave (initialization)	5m 40s
behave (kill_non_ha_replica)	12m 42s
behave (kill_primary)	41m 4s
behave (kill_replica)	40m 11s
behave (maintenance)	17m 14s
behave (op_track)	4m 48s
behave (pgconsul_util)	20m 21s
behave (plugins)	6m 38s
behave (primary_switch)	6m 21s
behave (priority)	13m 34s
behave (reset_sync)	5m 35s
behave (single_node)	5m 43s
behave (slot)	5m 19s
behave (start)	7m 16s
behave (switchover)	43m 55s
behave (targeted_switchover)	14m 11s
	7h 8m 23s

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