Handle missing parent interfaces

While this does not fix having inconsistent interfaces, at least we
don't fail enumerating them. With this change we still return these
children interfaces without parent set.

Bug: 159277702
Test: atest CtsLibcoreTestCases:libcore.java.net.NetworkInterfaceTest
Change-Id: Ibbe1f273683eb169a0e96425a2c21c5072bf19d7
Merged-In: Ibbe1f273683eb169a0e96425a2c21c5072bf19d7
2 files changed