src/rocksdb: switch back to master branch.

Signed-off-by: Mark Nelson <mnelson@redhat.com>

diff --git a/src/rocksdb b/src/rocksdb
index 9090ae3ecfbf9b50a398a5d8b178f14b88dc047e..bc7e8d472e7d37a33f3f45dec393769011ec1e08 160000 (submodule)
--- a/src/rocksdb
+++ b/src/rocksdb
@@ -1 +1 @@
-Subproject commit 9090ae3ecfbf9b50a398a5d8b178f14b88dc047e
+Subproject commit bc7e8d472e7d37a33f3f45dec393769011ec1e08