[MASSEMBLY-955] Add invoker test.

[wilx]

The test fails right now due to filtering issues described in MASSEMBLY-955.

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[wilx]

Cross reference: https://issues.apache.org/jira/browse/MASSEMBLY-955

[wilx]

@michael-o Ping.

[cstamas]

Test reused in UT here apache/maven-common-artifact-filters#25
This does not mean that this IT is to be dropped, but just FYI

[cstamas]

Locally verified: the new IT fails as is (as CI proves as well), but passes ok with apache/maven-common-artifact-filters#26

[INFO] Building: projects/dependency-sets/massembly-955/pom.xml
[INFO] run post-build script verify.bsh
[INFO]           projects/dependency-sets/massembly-955/pom.xml ... SUCCESS (4.0 s)

[cstamas]

Reusing this IT in another PR that opens soon

[cstamas]

Superseded by #68