cephfs/fuse: set big_writes default is false

The -o big_writes mount option has been removed in the libfuse 3.0
because it is now always active.
see: https://github.com/libfuse/libfuse/blob/master/ChangeLog.rst
so we big_writes default is false

Signed-off-by: huanwen ren <ren.huanwen@zte.com.cn>

src/common/options.cc

@@ -5472,8 +5472,8 @@ std::vector<Option> mds_client_options = {
   .set_description(""),
 
   Option("fuse_big_writes", Option::TYPE_BOOL, Option::LEVEL_ADVANCED)
-  .set_default(true)
-  .set_description(""),
+  .set_default(false)
+  .set_description("big_writes is deprecated in libfuse 3.0.0"),
 
   Option("fuse_atomic_o_trunc", Option::TYPE_BOOL, Option::LEVEL_ADVANCED)
   .set_default(true)