better handling for the case where an already-managed active item is rebinded active

do not clear the old location's record, and better logging
Make HA checker not promote again if node is stealing back master
Don't start feeds when in HOT_STANDBY/HOT_BACKUP
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/incubator-brooklyn
This closes #342