Fix the conditions for the tests based on comments on ag/15968818.

Check EXPECT_TRUE with status ok and Error none for valid display. and EXPECT_FALSE with status ok.
If service exists then we can proceed with test otherwise tests will be skipped.

Test: atest VtsHalGraphicsComposer3_TargetTest but tests don't just work yet. as we don't have service implementation.
BUG: 202053621
Change-Id: Iff8f4ca1e102ad8333ca63b0722b1fbd26414d06