Switch IpManager and IpReachabilityMonitor to use SharedLog

Test: as follows
    - built
    - flashed
    - booted
    - "runtest frameworks-net" passes
    - frameworks/opt/net/wifi/tests/wifitests/runtests.sh passes
    - frameworks/base/wifi/tests/runtests.sh passes
    - roamed from AP to AP watching IpRM logs accumulate
Bug: 62476366
Bug: 62162774

Change-Id: I155a26259420919eeed74166bacce3311caa49da