[dev fix] make fix_version unique
[dev fix] make fix_version unique

### What is this PR for?

Right now, if you merge PR into 2 branches, like, `master`, and `branch-0.9`, script
generates suggestion for "Fix Version" as `0.9.0,0.9.0`, because both master & 0.9 branch
are using the same base version.  This small fix leaves only unique values for suggested
version(s).

### What type of PR is it?
Development Improvement

Author: Alex Ott <alexott@apache.org>

Closes #3757 from alexott/make-version-list-unique and squashes the following commits:

53337e8aa [Alex Ott] [dev fix] make fix_version unique

joroKr21/incubator-zeppelin,zjffdu/zeppelin,VipinRathor/zeppelin,apache/incubator-zeppelin,apache/zeppelin,joroKr21/incubator-zeppelin,apache/zeppelin,jongyoul/incubator-zeppelin,hammertank/zeppelin,Leemoonsoo/incubator-zeppelin,prabhjyotsingh/incubator-zeppelin,jongyoul/zeppelin,zjffdu/zeppelin,apache/incubator-zeppelin,jongyoul/incubator-zeppelin,jongyoul/zeppelin,jongyoul/incubator-zeppelin,apache/zeppelin,jongyoul/zeppelin,zjffdu/zeppelin,fogbeam/zeppelin_mirror,jongyoul/zeppelin,Leemoonsoo/incubator-zeppelin,apache/incubator-zeppelin,VipinRathor/zeppelin,Leemoonsoo/zeppelin,apache/zeppelin,Leemoonsoo/zeppelin,hammertank/zeppelin,Leemoonsoo/zeppelin,prabhjyotsingh/zeppelin,Leemoonsoo/zeppelin,Leemoonsoo/zeppelin,fogbeam/zeppelin_mirror,joroKr21/incubator-zeppelin,joroKr21/incubator-zeppelin,jongyoul/zeppelin,joroKr21/incubator-zeppelin,VipinRathor/zeppelin,zjffdu/zeppelin,fogbeam/zeppelin_mirror,prabhjyotsingh/incubator-zeppelin,VipinRathor/zeppelin,prabhjyotsingh/zeppelin,VipinRathor/zeppelin,Leemoonsoo/incubator-zeppelin,prabhjyotsingh/zeppelin,zjffdu/zeppelin,jongyoul/incubator-zeppelin,Leemoonsoo/incubator-zeppelin,prabhjyotsingh/zeppelin,apache/incubator-zeppelin,joroKr21/incubator-zeppelin,apache/incubator-zeppelin,zjffdu/zeppelin,hammertank/zeppelin,Leemoonsoo/zeppelin,prabhjyotsingh/incubator-zeppelin,prabhjyotsingh/zeppelin,apache/zeppelin,hammertank/zeppelin,fogbeam/zeppelin_mirror,prabhjyotsingh/zeppelin,Leemoonsoo/incubator-zeppelin,apache/incubator-zeppelin,fogbeam/zeppelin_mirror,jongyoul/zeppelin,Leemoonsoo/incubator-zeppelin,prabhjyotsingh/zeppelin,prabhjyotsingh/incubator-zeppelin,apache/zeppelin,jongyoul/incubator-zeppelin,prabhjyotsingh/incubator-zeppelin,prabhjyotsingh/incubator-zeppelin,fogbeam/zeppelin_mirror,VipinRathor/zeppelin,jongyoul/incubator-zeppelin,hammertank/zeppelin,joroKr21/incubator-zeppelin,joroKr21/incubator-zeppelin,apache/zeppelin,jongyoul/zeppelin,fogbeam/zeppelin_mirror,Leemoonsoo/zeppelin,Leemoonsoo/zeppelin,hammertank/zeppelin,zjffdu/zeppelin,hammertank/zeppelin,VipinRathor/zeppelin