The fix to upload source versions of binary files when posting changes

that include parent diffs ended up causing warnings when attempting to

post a change that added a new binary file.
This change adds a check so we don't try to upload the source version of

a binary file if the source revision is PRE-CREATION.

Created a branch on top of another branch and made a commit that added a

new binary file. Posted the diff between the two branches and saw that I

did not see any warnings about trying to get the file content at the

PRE-CREATION revision.