libstatssocket_lazy: add isAvailable()

Early processes might not have access to libstatssocket. They should be
able to check before using libstatssocket APIs. Adding isAvailable().

Bug: 281162849
Test: atest libstatssocket_lazy_test
Test: atest StagedRollbackTest
Change-Id: Ie2a851ef5bcf4fe081898153d688a843d8886788
4 files changed