top: revise default for forest view child scans

top: revise default for forest view child scans

In an effort to avoid dangling children when in forest
view mode, top defaulted to a complete rescan of every
proc_t for each child encountered.

That expense was never really cost justified and now
with the 3.3 kernel 'hidepid' provisions it no longer
can offer such protection.

With this commit, the TREE_ONEPASS define is changed
to TREE_RESCANS so as to reverse the default scan
behavior.

Signed-off-by: Jim Warner <james.warner@comcast.net>