Block dynamic connection event if sensor not found

A bug in the Sensors HIDL spec marks onDynamicSensorsConnected as oneway
which means that HALs are not blocked on the framework processing that
event. This means the onDynamicSensorsConnected invocation and dynamic
meta event can be received out of order. Blocking processing of the
event gives time for onDynamicSensorsConnected to be invoked so that the
event can be correctly processed.

Bug: 201529167
Test: Connect dynamic sensor and validate that the HAL can deliver the
event and method invocation without any sleeps on the HAL side.

Change-Id: Ie1cad22f26de60a7cecb3c6048280c4919165dbb