Right now Queue Manager metrics are registered when the metrics struct
is created, which happens before a changed queue is shutdown and the old
metrics are unregistered. In the case of named queues or updates to
external labels the apply config will panic due to duplicate metrics.
Instead, register the metrics as part of starting the queue as we always
guarantee that Stop will be called before a new Start.
Signed-off-by: Chris Marchbanks <csmarchbanks@gmail.com>
b299aba6cf