Permission: Consistently treat exclusiveGroup as boolean
Permission: Consistently treat exclusiveGroup as boolean

At the moment exclusiveGroup is stored as boolean in Permission, but the
setter accepts a Boolean and the getter returns a Boolean.

This has some potential issues:
- the setter would fail with a NullPointerException if null was provided
- none of the callers of the getter is expecting null

Luckily this doesn't cause any real issues since
- all of the callers that deal with a Boolean have a null check and only
  invoke the method if it's not null
- the getter never returns null

Change-Id: Ia0cab62542442112b68732f0158459232fdff113
Signed-off-by: Edwin Kempin <d43fb6c98c97e553b671ed9a9318100f1de386e7@google.com>

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