Handle file send retry scenario inside thread to avoid ANR.

Use Case:
1. Turn on BT and pair with the other device via BT.
2. Launch Contacts ->press menu -> "Import/export" ->
   "Share visible contacts" -> "Bluetooth" -> "select
    paired device".
3. Turn off BT and let the transfer fail
4. Drag down the status bar and tap the bluetooth share notification
5. Wait for a while, tap "try again"

Failure:
ANR occurs and "Unfortunately,Bluetooth share has stopped" error comes.

Root Cause:
BluetoothOppSendFileInfo::generateFileInfo() takes long time to process
when there is huge contact list thereby causing ANR

Fix:
When tap the "try again" button on the send failed dialog, the
method "BluetoothOppSendFileInfo::generateFileInfo()" will be
call, if there are about 1500 contacts, then this method would
be very time consuming, therby causing ANR. Changed this method
into the child thread execution and through a Handler send a
message to the main thread after this method return, to retry failed
transfer.

Change-Id: Idde7e874e4e25caba59133e0981e812b06ba2ed1