Building via aggregator POM does not honor module's versions

**version**: 1.4.4

**usage context**:

- [x] maven command line: 3.6.1

**Problem description**:

When building several Maven projects - all with jgitver enabled - via aggregator POM (no jgitver there) the version numbers of the projects are not calculated and changed.

Rebroduce

- create aggregator pom with two modules A and B
- create subfolders A and B besides aggregator pom
- put an pom with only GAV in the subfolders
- put .mvn/extensions.xml in the subfolders
- git init / add / commit each subfolder
- git tag v1.3.0 each subfolder
- run mvn validate on aggregator pom

--> versions of projects A and B are not changed