Set BugreportProgressService to run on foreground.

BugreportProgressService do not persist the user-provided
information (like details and screenshot paths), so if it's killed by
the framework, that info is lost.

Running it as foreground mitigates the changes of it being killed.

BUG: 27431998
BUG: 28291423
Change-Id: I2f58507beb38309628f2f19d3f7f950d07eca16f