build-unit-tests: bump linux-headers revision

phosphor-ipmi-flash relies on the aspeed-p2a-ctrl linux header that is
only available in later revisions of openbmc/linux.

Change-Id: I76725c1020b4f190d9b214f985d9190356723406
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/build-unit-test-docker.sh b/build-unit-test-docker.sh
index 683cdb6..e38b73a 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -99,8 +99,8 @@
   [json]=v3.3.0
   # Snapshot from 2019-01-11
   [lcov]=04335632c371b5066e722298c9f8c6f11b210201
-  # dev-5.0 2019-03-26
-  [linux-headers]=c8733f5abd0656acfef17d462e72ef105db9924d
+  # dev-5.0 2019-05-03
+  [linux-headers]=8bf6567e77f7aa68975b7c9c6d044bba690bf327
   # libvncserver commit dd873fce451e4b7d7cc69056a62e107aae7c8e7a is required for obmc-ikvm
   # Snapshot from 2018-10-08
   [libvncserver]=7b1ef0ffc4815cab9a96c7278394152bdc89dc4d