xmvn produces unreproducible output

[bmwiedemann]

While working on reproducible builds for openSUSE, I found that
xmvn creates .xml files with randomness
per setUuid( UUID.randomUUID().toString() )
in
xmvn-tools/xmvn-install/src/main/java/org/fedoraproject/xmvn/tools/install/JavaPackage.java
xmvn-tools/xmvn-install/src/main/java/org/fedoraproject/xmvn/tools/install/impl/DefaultArtifactInstaller.java

+++ new//usr/share/maven-metadata/jackson-parent.xml    2019-11-20 12:00:00.0000
00000 +0000
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <metadata xmlns="http://fedorahosted.org/xmvn/METADATA/3.0.0">
-  <uuid>84081e46-b2dd-41c9-b0e1-3e89752c546d</uuid>
+  <uuid>c67ba8dc-3f70-4b4e-95b4-c0afdf000afe</uuid>
   <artifacts>

previously filed at https://bugzilla.opensuse.org/show_bug.cgi?id=1162112