MB-8429: grab memcached logs in osx too

Clearly grabbing memcached logs is not Linux-specific and thanks to
"server guts" we should have right path regardless of OS or customer
setup.

Change-Id: Ie8320b9a872c035b9b8a809b6caf86e6f02e8022
Reviewed-on: http://review.couchbase.org/26841
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Revert "Revert "MB-8415 change engine...""

This reverts commit a165d1c10cf0071571cd3787a0b7c5a5cae3f391.

This returns original commit which was just reverted in order to let
ep-engine folks review their corresponding change.

Change-Id: Ied466f51f2ee648c350e1b2b490bbe78576f624b
Reviewed-on: http://review.couchbase.org/26787
Reviewed-by: Jin Lim <jin@couchbase.com>
Tested-by: Jin Lim <jin@couchbase.com>
MB-8415 set minum num_threads back to 2 and set default to 3

Change-Id: Ib82f15f31155dd8f9e4f37073b27115f300549d2
Reviewed-on: http://review.couchbase.org/26796
Reviewed-by: Jin Lim <jin@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Jin Lim <jin@couchbase.com>
Merge remote-tracking branch 'origin/2.1.0'

* origin/2.1.0:
  MB-8415 set minum num_threads back to 2 and set default to 3
  Revert "Revert "MB-8415 change engine...""
  MB-8429: grab memcached logs in osx too

trivial merge

Change-Id: I88dfd7d599b7af47d28b708daf9dd4fae4cdabfb