Fix bootchart

Found the following 2 binary is not in the path
system/core/init/grab-bootchart.sh: line 20: bootchart: command not found
system/core/init/grab-bootchart.sh: line 21: gnome-open: command not found

Use a more commonly available command to create bootchart

Test: system/core/init/grab-bootchart.sh started a bootchart
successfully

Change-Id: I6d5b4a692af2fd53ea636b768f55c697586e6898