SuspendSepolicyTests: Ignore already labeled wakeup nodes

SuspendSepolicyTests tries to clean up genfs_contexts
by labeling a common parent wakeup path if one exists,
instead of all the child paths.

Don't fail if all the child paths are labelled but the
common parent directory isn't

Bug: 293232770
Bug: 297945473
Test: atest SuspendSepolicyTests
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:d32d12bb20112986049f00ca699c3d0ae59a1a84)
Merged-In: I7eb8185821ca7bb277604a67c5443fd5e503e4ea
Change-Id: I7eb8185821ca7bb277604a67c5443fd5e503e4ea