mResult in SinglePackageBackupPreflight could be set to a negative value if preflight timeouted. Together with ag/863259 this change will better handle this case. Bug: 26818914 Change-Id: I171bf95f146552b3b50f044964c2b041f6303d90 (cherry picked from commit a235f7e4e046b1a69af988240ff5f0dd46f3b5f9)