Theme compat: When resetting post, set 'is_page' to true.

Previously, when resetting the post, 'is_archive' was set to true.

As a consequence, certain themes with some form of conditional
template logic (like Atahualpa and Attitude) were loading their
archive template because of the 'is_archive' flag.  This caused
formatting display issues because the archive template historically
uses the_excerpt() causing all formatting to be stripped out.

This commit changes all reset post calls so the 'is_page' parameter is
set to true.  This should correctly use the regular page template for
theme compatibility for themes with conditional template logic.

See #5301.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7736 cdf35c40-ae34-48e0-9cc9-0c9da1808c22