CA-334613: Clip region within which performance graph lines are drawn
CA-334613: Clip region within which performance graph lines are drawn

Sharp turns in the graph can result in the line being drawn outside of the box.
This change makes sure the line is only rendered within the input rectangle.

Signed-off-by: Danilo Del Busso <766dc0f994b57f2d2e98930ecfa5ee8fb1091a62@citrix.com>

xenserver/xenadmin,kc284/xenadmin,xenserver/xenadmin,xenserver/xenadmin,kc284/xenadmin,kc284/xenadmin,kc284/xenadmin,kc284/xenadmin