Renaming bugreport.txt to bugreportFile.getName()

Many times to file a bug, its necessary to take several bugreports and
attach them all to the same bug.  With the current implementation, all
extracted files are bugreport.txt which makes it difficult to attach
several bugreports to the same bug, and reference them throughout the
bug uniquely.

Bug: 20447313
Change-Id: I22d2286d06c8dfb82273b5b98c48b21f77941b15