MB-24055: Change ht_size to 47; ht_resize_interval to 1s

MB-24055: Change ht_size to 47; ht_resize_interval to 1s

To determine a good tradeoff between initial memory usage and
rebalance speed, the following tests were performed:

    ht_size	    ht_resize_interval (sec)  Rebalance time (min)  Initial RSS (MB)
    3079 (default)  60 (default)	      4.5                   74.4
    769             1	                      3.8                   52.2
    193	            1                         4.3                   47
    47	            1                         4.1                   45.5
    13	            1                         4.4                   45

Based on these results a ht_size of 47 (with resize_interval==1) has
been picked - this gives rebalance time as good as current; but with a
39% reduction in initial memory usage.

Change-Id: I329e18240bace9f4905e3eb0c4d59abd97dd8cd1
Reviewed-on: http://review.couchbase.org/77892
Reviewed-by: Jim Walker <jim@couchbase.com>
Reviewed-by: Manu Dhundi <manu@couchbase.com>
Tested-by: Build Bot <build@couchbase.com>