Debug.isVmapStack reads kernel configs only

... but not other runtime VINTF info. This may or may
not fix the nullptr exception when accessing getRuntimeInfo().

In either case, this change should improves code health in general:
- it avoids reading things it doesn't need
- it avoids copying the map

Bug: 151092221
Test: m libandroid_runtime -j

Change-Id: I6cb9052eb56fd83ef7ee81751d9791533a36aeed