Remove constructors and defer creating the Handler to onBind.

Previously, the Handler couldn't be built because we tried to call
getMainLooper() before the Service's base context was attached.

Bug: 268741053
API-Coverage-Bug: 265968015
Test: atest SharedConnectivityServiceTest
Change-Id: I70caac89ca69545e62b177872ef144b031cc4846
3 files changed