'rc' releases fail on CI

[lukaszstolarczuk]

In CI script, function run_example is trying to locate the produced jar file... and is greping files using regex - this is not working properly with RC or SNAPHOST versions (e.g. 1.2.1-rc1). On RC tags the CI will constantly fail.

It should be fixed, e.g., by changing the mentioned function, to behave similarly to our example's README: https://github.com/pmem/pmemkv-java/tree/master/examples#pmemkv-examples