get a stable rocksdb (3.0)

Signed-off-by: xinxin shu <xinxin.shu@intel.com>

diff --git a/src/rocksdb b/src/rocksdb
index a1a1f61fa75e35340ec64624234f9b68520545b4..2b3260d5dd439edcb460f606fc48f226645d8111 160000 (submodule)
--- a/src/rocksdb
+++ b/src/rocksdb
@@ -1 +1 @@
-Subproject commit a1a1f61fa75e35340ec64624234f9b68520545b4
+Subproject commit 2b3260d5dd439edcb460f606fc48f226645d8111