mds: disable `defer_client_eviction_on_laggy_osds' by default

[mgfritch]

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

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[trociny]

nit: I would prefer it as git cherry-pick -x 109de8bdab86e1adaad580d9e7322c18fa01bc09 so we have information in git history that this is not SUSE specific.

[mgfritch]

nit: I would prefer it as git cherry-pick -x 109de8bdab86e1adaad580d9e7322c18fa01bc09 so we have information in git history that this is not SUSE specific.

I had to re-implement the fix, because the patch doesn't apply to pacific branch, but I've added the cherry-pick message to the commit anyway

[trociny]

I had to re-implement the fix, because the patch doesn't apply to pacific branch, but I've added the cherry-pick message to the commit anyway

I see. The upstream approach in this situation is still to cherry-pick, resolve the conflict manually and add a note about the conflict to the log message. Anyway, LGTM, thanks.