mongoose: fix warning

Signed-off-by: Sage Weil <sage@inktank.com>

diff --git a/src/mongoose b/src/mongoose
index 173c277c6991e4f2c880ca885245f4a07d14160b..ca7d69fda0cd806b8b52debfa814b493d6dee3c1 160000 (submodule)
--- a/src/mongoose
+++ b/src/mongoose
@@ -1 +1 @@
-Subproject commit 173c277c6991e4f2c880ca885245f4a07d14160b
+Subproject commit ca7d69fda0cd806b8b52debfa814b493d6dee3c1