PeerConnection owns the PacketSocketFactory dependency.

The PacketSocketFactory dependency (if present on the object passed to
CreatePeerConnection(...)) is given as a raw pointer to the
PortAllocator, but the unique_ptr remains in the dependencies object
which is destroyed at the end of the Initialize call.

Bug: webrtc:11467
Change-Id: I2ccb22b6313fc6b2887bb581704f73a703092af3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/172043
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Taylor <deadbeef@webrtc.org>
Commit-Queue: Jorge Moreira Broche <jemoreira@google.com>
Cr-Commit-Position: refs/heads/master@{#30953}