Make the runtime default to not allowing JDWP again.

This was unintentionally changed a while ago and is causing a CTS test
to fail. Changed to make the runtime default to disabling jdwp if a
provider isn't given. Note this does not stop one from starting a
debugger with -agentpath. If jdwp options are given with jdwp disabled
the runtime will print a warning.

Test: atest CtsJdwpSecurityHostTestCases
Test: ./test/run-test --host --debug 001-HelloWorld
Bug: 72400560

Change-Id: I6561f269d9279eba0c1ac0b0f593ece867dab49e