Fix flaky GNSS VTS

In the original code, vector::erase() would invalidate iterators so we
should move the thread object into the std::async() for the blocking
operation.

Bug: 344250967
Test: atest VtsHalGnssTargetTest
Change-Id: I4cc82131bb070a37cb6ed9dbe9d7cccc7ab5ee89
2 files changed