Bug 990392: Make |sIsPairing| non-atomic, r=echou

|sIsPairing| is not a shared resource. No need to make it atomic.
Bug 990392: Move sAuthorizedServiceClass to I/O thread, r=echou

|sAuthorizedServiceClass| is being set on the main thread, but read
from within the I/O thread. Making the variable a static constant
array and moving all access to the I/O thread fixes potential race
conditions.
Bug 990392: Cleanup |GetServiceChannel| in BluetoothDBusService, r=echou

This patch prepares moving |sAdapterAdded| to the I/O thread. For
|GetServiceChannel| it gets pushed into task classes on the I/O
thread and the interface of these classes is cleaned up.
Bug 990392: Move |sAdapterPath| to I/O thread, r=echou

|sAdapterPath| is being accessed from within the main and the
I/O thread in a possible non-thread-safe way. This patch moves
all access to the I/O thread.
Bug 990392: Move |sControllerArray| to main thread, r=echou

|sControllerArray| is only being used on the main thread, but
cleared on the I/O thread. During the BlueZ shutdown, we go
through the main thread, where we can clear |sControllerArray|;
moving the variable to main thread exclusively.
Bug 990392: Fix comments about shared variables in BluetoothDBusService, r=echou