Merge "vpn: Fix NPE in VpnConfig#toString when no ProxyInfo is set" into rvc-dev am: 4cf6815168 am: da7b5b0b09 am: 4b6b970787 am: 0230c6e2e7

Change-Id: I10de38c137ba8c5d23c10d3e6adbdd0c25add610