MB-12271: Set the default dcp producer noop interval to 20 seconds

This is a fix to support backwards compatibility between 3.0 and
3.0.1+ versions of Couchbase. The problem is that 3.0 has a noop
interval of 20 seconds by default and 3.0.1 has a default noop
interval of 200 seconds. In 3.0.1 the consumer explicitly sets
the noop interval of the producer so in 3.0.1+ clusters the 20
second default will be overriden by the consumer, but in the
scenario when a 3.0.1+ node connects to a 3.0 node the 20 second
default will remain.

Change-Id: I2e18e9ad68037f3a82abe5167f2bca89f381f318
Reviewed-on: http://review.couchbase.org/42136
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>
MB-12226: Handle ENOENT error during unlink

If the file is not found during an unlink, it shouldn't be added
to the pending file deletions queue.

Change-Id: Ief306277bbbc946ae18e39dd4819f811f12ea76c
Reviewed-on: http://review.couchbase.org/42173
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Sriram Ganesan <sriram@couchbase.com>
Hide the -a argument in cbstats

The -a argument is used by cbcollectinfo so we can't just
get rid of it.

Change-Id: I0f04c2d454c117271b44176df904e90a938965e9
Reviewed-on: http://review.couchbase.org/42297
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>
Merge remote-tracking branch 'couchbase/3.0.1'

Change-Id: Iea18be488592f879e6eaa5b8bc16cf9d33836a58