adding abs() functions when creating the values to be graphed since the graph only handles positive values.
Does not apply to FT_RELATIVE_TIME.

This is being added to master-1.12 to avoid breaking future QT functionality in the graph.

Bug 9985 - Add absolute values to i/o graph

Change-Id: I32565c346bef48ec852f61c379df96f2c733e68f
Reviewed-on: https://code.wireshark.org/review/2780
Reviewed-by: Evan Huus <eapache@gmail.com>