Fix "Attempt to delete released memory" warning.

EXPECT_NONFATAL_FAILURE(statement, ...) expands to
  do {
    ... statement ...
  } while (::testing::internal::AlwaysFalse());

Clang analyzer cannot see into AlwaysFalse(),
and gives a false warning assuming that the
do loop can be done twice.

Use a unique_ptr::reset to call delete,
because reset can be called multiple times..

Bug: 259999410
Test: make tidy-system-core-fastboot_subset
Change-Id: Ie536f76635dd55f4e47b80eed6498fd1193b88ee