Unhide ICMP echo constants.

Bug: 129251251
Test: atest android.net.ipv6.cts.PingTest com.android.cts.net.hostside.VpnTest com.android.cts.deviceandprofileowner.AlwaysOnVpnTest
Change-Id: I5dc8fce0ac47aa622c8d6763b8fa443a7a0570c8
1 file changed