Mechanical code cleanup (messagebus-spi)

Mechanical code cleanup (messagebus-spi)

* Remove unnecessary type specifiers (use Java 7 <>)
* Remove unnecessary "extends Object" declarations
* Remove unnecessary semi-colons
* Merge identical catch blocks
* Remove redundant modifiers:
  - enum constructors are private by default
  - interface properties are public static final by default
  - interface methods are public abstract by default
  - interfaces are abstract by default
  - inner interfaces are static by default
  - inner classes in interfaces are public static by default

Change-Id: I75e706701f0bd63fd483079aa59ee4da8b88e0e4
Signed-off-by: Stephen Kitt <skitt@redhat.com>