packaging: Use POM_VERSION to locate artifacts

We currently use APP_VERSION to locate artifacts in the directory where
they are deployed during the build, but this doesn't work if APP_VERSION
is different to the version specified in the root POM.

Change-Id: I6b780190ccb2c71b40f43f4697cd04c061fca9ad
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>