Add missing swift constraint for functional tests

Looks like we are keeping at least four lists of the default
constraints in various places, and when we added the max_header_size
in initial Static Large Object Support commit (5d73da15) we failed to
add it to the two locations in the test tree (test/sample.conf and
test/functional/tests.py).

With this commit we take a small step to consolidate the list of
constraints to the constraints module by removing the list from the
tests module (note we still have them listed in the sample swift.conf
file and the test module's sample.conf file), document the missing
reference in the test module's sample.conf file, and, while we're at
it, use the SWIFT_CONF_FILE reference where possible.

Change-Id: Ic4fa5f1aedec9bc7a7b43ce1a2ca3cdebce6171f
Functional tests for TempURL and SLO together

Change-Id: I4893911e50005d5b669b96e7d59b6149c734780e
Fix ring-builder crash

If you had a partition with 1 replica on a deleted device, 1 on a
zero-weight device, and 1 on a normal device, then rebalancing would
crash. This was because the ring builder was memoizing tiers_for_dev()
for all *available* devices (i.e. weight > 0 and not deleted), but
depended on it being present for all devices with partitions still on
them.

Since the builder moved the replica from the deleted device, it left
the one on the zero-weight device alone, so you had an unavailable
device with a partition replica still on it, triggering the crash.

Now we go ahead and memoize tiers_for_dev() for *all* devices, not
just available ones, thereby fixing the crash.

Change-Id: Ie0b58b65e0353732cf785ab772e95e699f3a5b5d
Merge "Add missing swift constraint for functional tests"
Merge "Functional tests for TempURL and SLO together"
DRY out common.constraints a bit more

Change-Id: If8a71692b79e381036b34245e09697ac1009beca
Merge "Fix ring-builder crash"
Merge "DRY out common.constraints a bit more"