Update seastar submodule
Update seastar submodule

* seastar 11e86172ba...5db34ea8d3 (7):
  > scollectd: Avoid a deprecated warning
  > prometheus: Avoid protobuf deprecated warning
  > Merge "Avoid abandoned futures in tests" from Rafael
  > Merge "make circular_buffer methods noexcept" from Benny
  > futures_test: Wait for future in test
  > iotune: Report disk IOPS instead of kernel IOPS
  > io_tester: Ability to add dsync option to open_file_dma

avikivity/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla