MB-10058 Remove code ignoring certain number of memcached errors.

The referred bug was fixed in 2.5 by lowering the number of ingored
errors to 0. Here I completely removed this code path.

Change-Id: I26e7679be5ead20f929424567cdea10eaba5a6f3
Reviewed-on: http://review.couchbase.org/33420
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
MB-10127 Get rid of enable_pipeline_ops setting.

Because pipelining should be used and is used all the time anyway.

Change-Id: I6f6aca83ab21654cbb7ad9fedd79c388ac559e92
Reviewed-on: http://review.couchbase.org/33421
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
MB-10127 Always use memcached connection pool for xdcr.

Change-Id: I2746cf398202143a81ced5d6147fcdb205a4e8fa
Reviewed-on: http://review.couchbase.org/33422
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>