license metadata performance

Tune the top-down walk to avoid needlessly walking the same subtree
over and over again with the same condition(s).

Takes walking system image down from 3m to 1.5s.

Test: m all systemlicense listshare checkshare dumpgraph dumpresolutions

Bug: 68860345
Bug: 151177513
Bug: 151953481

Change-Id: I4354800cd8dfc42efd4df274d2ce45eaa3e0a99f