Get File Wrong Content-Type Bug Fix

JIRA: CBDEUCE-99
- pep8 compliance
Get File Wrong Content-Type Bug Fix

- Enhancement: We don't need the try/except handling in the vault model as it's handled by the drivers so only sane values (0+) come back
Get File Wrong Content-Type Bug Fix

JIRA: CBDEUCE-99

- Enhancement: Added test for file size of non-existent file; result should be zero