Apply mtu and selected IPv4 address to tun interface. Then, bring up the tun interface. Bug: 212345928 Test: flash and boot Run "atest ClatCoordinatorTest" in a followup commit. Change-Id: I24a2a91e2b084be28820a7a63b265c5f56293334
Apply mtu and selected IPv4 address to tun interface. Then, bring up the tun interface. Bug: 212345928 Test: flash and boot Run "atest ClatCoordinatorTest" in a followup commit. Change-Id: I24a2a91e2b084be28820a7a63b265c5f56293334