Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Merge "Update the link to firewall_block_image.img"
  - Update the link to firewall_block_image.img

    As the link http://205.177.226.237:9999/onosfw/firewall_block_image.img
    has been deprecated, now the valid link is updated, aiming at running the
    testcase onos_sfc.

    JIRA: FUNCTEST-820

    Change-Id: Id848e3ab92c3b0fb47e3c755d203844dd94d8408
    Signed-off-by: Linda Wang <wangwulin@huawei.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index e32f797..4ec87bd 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit e32f797894cbc66a73976e50bcdb8e59f02eedc2
+Subproject commit 4ec87bd88fe9b176a61ff13b5e50b8ede4f3498f