Process: allow closed target fd.

The comment suggest that the fstat() check is to simplify the logic to
dup2, this patch switch to use base::ShuffleFileDescriptors() to handle
that logic so that we can allow closed fd.

Bug: 121177337
Test: unit tests
Change-Id: I9fdb0cd00fb371ebcd90a3d6e91a353159ab8413
2 files changed