dumpstate: add dropbox crashes to bugreport

Adds system crashes from the dropbox to the end of the bugreport
to allow diagnosing issues even after the device has rebooted.

Test: adb bugreport
Bug: 36852229
Bug: 26849505
Change-Id: I11589b81208e916d25d543c43c1283bdbffda949
1 file changed