MB-8102:  fix moxi segfault due to overflowed file descriptors

replaces abandoned http://review.couchbase.org/#/c/30424/

Change-Id: I5b91d204cf334fc600d4799da95f7f2ed1d76cd4
Reviewed-on: http://review.couchbase.org/30431
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>