man: Fix corosync.conf knet pong count default

commit 029b8ebad60314d3daa285eb945c55355fade389 changed the default
of the KNET_PONG_COUNT from the kronosnet default of 5 to 2, as
corosync bring up was deemed to slow.

The documentation, and the comment stating that the totem config
default values match the knet ones were not updated, and thus now out
of date.

Fixhis by noting the correct default of 2 for KNET_PONG_COUNT and
note that all but that one are in sync with the korosync defaults in
the comment.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Reviewed-by: Jan Friesse <jfriesse@redhat.com>