mds: disable `defer_client_eviction_on_laggy_osds' by default

This config can result in a single client holding up mds to service
other clients since once a client is deferred from eviction due to
laggy OSD(s), a new clients cap acquire request can be possibly
blocked until the other laggy client resumes operation, i.e., when
the laggy OSD is considered non-laggy anymore.

Disable the config by default till the issue is fixed.

Fixes: http://tracker.ceph.com/issues/64685
Signed-off-by: Venky Shankar <[email protected]>
(cherry picked from commit 109de8b)

Conflicts:
	src/common/options/mds.yaml.in

src/common/options.cc

@@ -9023,7 +9023,7 @@ std::vector<Option> get_mds_options() {
      .set_long_description("The maximum number of entries before any new entries are rejected with ENOSPC."),
 
     Option("defer_client_eviction_on_laggy_osds", Option::TYPE_BOOL, Option::LEVEL_ADVANCED)
-     .set_default(true)
+     .set_default(false)
      .set_flag(Option::FLAG_RUNTIME)
      .set_description("Do not evict client if any osd is laggy")
      .set_long_description("Laggy OSD(s) can make clients laggy or unresponsive, this can lead to their eviction, this option once enabled can help defer client eviction."),