Make NetworkInterface.isUp() test for IFF_RUNNING.

This makes java.net.NetworkInterface.isUp() return true only if the
interface has both IFF_UP and IFF_RUNNING flags set. This restores the
behaviour of nougat[1], and makes the behaviour match the javadoc. The
behaviour in oreo[2] was changed during a rewrite[3] which replaced
the native implementation with a pure java implementation that dropped
the IFF_RUNNING check (compare the new java code with the removed
native code). There is no evidence that this behaviour change was
intentional.

This change also reverts the changes to CTS made for oreo to work
around the behavioural change.

This reverts commit acd3bea0.

[1] https://android.googlesource.com/platform/libcore/+/nougat-release/ojluni/src/main/native/NetworkInterface.c#393
[2] https://android.googlesource.com/platform/libcore/+/oreo-release/ojluni/src/main/java/java/net/NetworkInterface.java#452
[3] https://android-review.googlesource.com/c/platform/libcore/+/231080

Bug: 71977275
Test: cts-tradefed run cts-dev -m CtsLibcoreTestCases
Change-Id: I75066e49c5f864828adc928cc3687311f2f05011