Unable to limit number of REPLICATE requests per drive

[clayg]

SSYNC requests can be limited per-device via the object-server config options:

# Set to restrict the number of concurrent incoming SSYNC requests
# Set to 0 for unlimited
# Note that SSYNC requests are only used by the object reconstructor or the
# object replicator when configured to use ssync.
# replication_concurrency = 4
#
# Set to restrict the number of concurrent incoming SSYNC requests per
# device; set to 0 for unlimited requests per device. This can help control
# I/O to each device. This does not override replication_concurrency described
# above, so you may need to adjust both parameters depending on your hardware
# or network capacity.
# replication_concurrency_per_device = 1

We need to have options for:

replicate_concurrency and replicate_concurrency_per_device

... or else when a object-replicator disconnects because a REPLICATE request is taking too long the object-server still gets stuck handling the request and the whole mess just backs things up more.