Update git submodules

* Update docs/submodules/bgpcep from branch 'master'
  to cf8410dbfd1b2fff815e3f9cc0182a45157a58da
  - Rework Cluster-Id config

    BGPCEP-564
    Change-Id: I96557eca0c599e0934b7fada91bfc35162eae7bc
    Signed-off-by: Claudio D. Gasparini <claudio.gasparini@pantheon.tech>
  - Delete routes under eff-rib-in

    only if there are present.

    Change-Id: I7c863999b54a16dec2bcaddd256c6ff7121b0cb5
    Signed-off-by: Claudio D. Gasparini <claudio.gasparini@pantheon.tech>
  - Rework OffsetMap.remove() and share empty arrays

    Empty arrays are immutable, hence we can share those instances,
    reducing overheads. Also updates OffsetMap.remove() to take an
    empty array argument, which will be used when the map would become
    empty.

    Change-Id: I58116eddce3d8b1a1f7d049c0c1f12fcd9f79966
    Signed-off-by: Claudio D. Gasparini <claudio.gasparini@pantheon.tech>
    Signed-off-by: Robert Varga <robert.varga@pantheon.tech>

diff --git a/docs/submodules/bgpcep b/docs/submodules/bgpcep
index 962b0b9dab61baea3019aaf6ddff0fd5fe84cd72..cf8410dbfd1b2fff815e3f9cc0182a45157a58da 160000 (submodule)
--- a/docs/submodules/bgpcep
+++ b/docs/submodules/bgpcep
@@ -1 +1 @@
-Subproject commit 962b0b9dab61baea3019aaf6ddff0fd5fe84cd72
+Subproject commit cf8410dbfd1b2fff815e3f9cc0182a45157a58da