BLE: Don't start scan if the same Pi scan is running.

For some APP, will trigger pending intent BLE scan when the APP start
but doesn't stop pending intent BLE scan. After long time, it will use
more client_if cause BLE scan leak. For the use case, don't start
pending intent BLE scan if the same scan is running.

Bug: 143014582
Test: Trigger two or more Pi BLE scan with same intent information.

Change-Id: Id032025e1276cd87626bd81e235078820948d909
Merged-In: Id032025e1276cd87626bd81e235078820948d909