Prefer variants test-only:true attribute when grouping.

When looking at more details of modules that are marked test-only, I saw
that `java_test_host` modules were not in the list.

The test I wrote for it passes, but in a real run, there are two variants (one
windows, one linux) which causes it to fail.  The `all_teams` code visis
all variants, even not enabled ones. The windows variant, for which
GenerateAndroidBuildActions was not being called, did not have a
provider and its empty data was overriding the variant for which we had
data.

I changed the code to prefer variants where it is true.
Generally for "test-only", the value is logically true independent of variant, so
if one variant sets it true, it should be considered true for all
variants.
I think this is a slightly better check than preferring a variant with a
provider or that is enabled.

Prev CL
       % gqui from  "flatten(~/aosp-main-with-phones/out/soong/ownership/all_teams.pb, teams)" proto team.proto:AllTeams 'select teams.kind, count(*) where teams.test_only = true and teams.kind not like "%cc_%" group by teams.kind'
        +--------------------------+----------+
        |        teams.kind        | count(*) |
        +--------------------------+----------+
        | android_test             |     1382 |
        | android_test_helper_app  |     1680 |
        | java_fuzz                |        5 |
        | java_test                |      774 |
        | java_test_helper_library |       29 |
        +--------------------------+----------+

After
	 gqui from  "flatten(~/aosp-main-with-phones/out/soong/ownership/all_teams.pb, teams)" proto ~/aosp-main-with-phones/build/soong/android/team_proto/team.proto:AllTeams ' select teams.kind, count(*) where teams.test_only = true and teams.kind not like "%cc_%" group by teams.kind'
	+--------------------------+----------+
	|        teams.kind        | count(*) |
	+--------------------------+----------+
	| android_test             |     1382 |
	| android_test_helper_app  |     1680 |
	| csuite_test              |       16 |
	| java_fuzz                |       10 |
	| java_test                |      774 |
	| java_test_helper_library |       35 |
	| java_test_host           |      495 |
	+--------------------------+----------+

Test: go test ./android
Test: m all_teams
Test: m blueprint_tests
Change-Id: Idc5ed1c0375dc7390a0d58fcb4bf0d7fe1c7ab4f