seastar: pick up a recent seastar

to alleviate the pain of keeping in sync with seastar upstream.

Signed-off-by: Kefu Chai <kchai@redhat.com>

diff --git a/src/seastar b/src/seastar
index 663f9bb6cb2b20feb8448674eaa6a743cd513e5a..0523b0fac4123f4998f3c7af0a3d8110fc1bc675 160000 (submodule)
--- a/src/seastar
+++ b/src/seastar
@@ -1 +1 @@
-Subproject commit 663f9bb6cb2b20feb8448674eaa6a743cd513e5a
+Subproject commit 0523b0fac4123f4998f3c7af0a3d8110fc1bc675