[flexbridge] Fix usage of upload_target
[flexbridge] Fix usage of upload_target

* Rename to make it clear whether using the upload_target groovy
variable or a variable in bash, now renamed to upload_suite.
* Remove variable set for make-source since not needed.
* Escape dollar on bash variable name to pass dollar thru to bash so
upload_suite is substituted at build time rather than when the jenkins
job is created.

Change-Id: Id34fd9b4cabf2c9219fe41e12589e24e0772757c

sillsdev/ci-builder-scripts,sillsdev/ci-builder-scripts,sillsdev/ci-builder-scripts