(Take two) Do not hold lock when calling into NotificationManager

setNetworkLoggingActiveInternal() is being called at a few places
where lock has already been acquired, so it's not sufficient to
just move around NotificationManager calls within
setNetworkLoggingActiveInternal. Post those calls to a handler
thread as a quick fix for now.

Bug: 192435507
Test: atest DeviceOwnerTest#testAdminActionBookkeeping
Test: atest DeviceOwnerTest#testNetworkLoggingWithSingleUser
Test: atest DeviceOwnerTest#testNetworkLogging_multipleBatches
Test: atest DeviceOwnerTest#testNetworkLoggingWithTwoUsers
Test: atest DeviceOwnerTest#testNetworkLogging_rebootResetsId
Test: atest OrgOwnedProfileOwnerTest#testNetworkLoggingLogged
Test: atest OrgOwnedProfileOwnerTest#testNetworkLoggingDelegate
Test: atest OrgOwnedProfileOwnerTest#testNetworkLogging
Test: atest DeviceOwnerPlusProfileOwnerTest#testNetworkAndSecurityLoggingAvailableIfAffiliated
Test: atest MixedDeviceOwnerTest#testDelegation
Test: CTSVerifier: Device Owner Tests -> Network Logging U
Change-Id: I34d90c933525a9bf31a1ab9a40866006790796ad