ncsid: Use PACKET_MR_PROMISC

Using IFF_PROMISC is dangerous because it requires us to set the IF
flag. The if flags cannot be set atomically, and they are expected to be
owned and managed by systemd-networkd. NCSId will sometimes race with
systemd-networkd and discard the IFF_UP flag and prevent the interface
from coming up during boot.

PACKET_MR_PROMISC does not depend on the flags and will not conflict
with other processes using the interface.

Change-Id: I4c193e73bff789e079e859d2b98c2477b2956d54
Signed-off-by: William A. Kennington III <wak@google.com>
2 files changed