A Google modification to eglCreateWindowSurface was
causing SurfaceFlinger to set its swap interval
value back to 1, regardless of the value set in the
debug.gr.swapinterval property.
This patch modifies the fb_setSwapInterval function
in gralloc to check the debug.gr.swapinterval
property and not change the swap interval if a value
is set there.
CRs-fixed: 329524
Change-Id: I80463c1209addbff227db7832dd0023e94eb06ac
d6b1474f2d