upload: fix display of destination branch for SingleBranch

The command `repo upload --cbr -D <some branch>` will display
the default revision, and not the actual destination branch.

Fix that and display the branch to which the change will be
uploaded to.

Change-Id: I712ed0871c819dce6774c47254dac4efec4532e0

subcmds/upload.py

diff --git a/subcmds/upload.py b/subcmds/upload.py
index fc17670..f5833dd 100644
--- a/subcmds/upload.py
+++ b/subcmds/upload.py
@@ -189,7 +189,7 @@
       date = branch.date
       commit_list = branch.commits
 
-      destination = project.dest_branch or project.revisionExpr
+      destination = opt.dest_branch or project.dest_branch or project.revisionExpr
       print('Upload project %s/ to remote branch %s:' % (project.relpath, destination))
       print('  branch %s (%2d commit%s, %s):' % (
                     name,