Update git submodules

* Update swift from branch 'master'
  to 9fb75e5af57cc8d7282951f55ecc8d0e16d983cf
  - Merge "slo: use Timestamp.zero() as default in RespAttrs"
  - slo: use Timestamp.zero() as default in RespAttrs

    Also make test assertions for async delete at times less
    brittle.

    Change-Id: I750ac1ab2a75d1a49c87c6e1704ebe733fb31ec2
    Signed-off-by: Alistair Coles <alistairncoles@gmail.com>

diff --git a/swift b/swift
index 124cdcba668a402bc40c9a0aa20c2f46abfbb7a4..9fb75e5af57cc8d7282951f55ecc8d0e16d983cf 160000 (submodule)
--- a/swift
+++ b/swift
@@ -1 +1 @@
-Subproject commit 124cdcba668a402bc40c9a0aa20c2f46abfbb7a4
+Subproject commit 9fb75e5af57cc8d7282951f55ecc8d0e16d983cf