Don't test forward compatibility in qpy compat tests

test/qpy_compat/process_version.sh

@@ -14,9 +14,23 @@
 set -e
 set -x
 
+# version is the source version, this is the release with which to generate
+# qpy files with to load with the version under test
 version=$1
 parts=( ${version//./ } )
-if [[ ${parts[1]} -lt 18 ]] ; then
+# qiskit_version is the version under test, We're testing that we can correctly
+# read the qpy files generated with source version with this version.
+qiskit_version=`../qiskit_venv/bin/python -c "import qiskit;print(qiskit.__version__)"`
+qiskit_version_pars = ( ${qiskit_version//./ } )
+
+# If source version is less than 0.18 QPY didn't exist yet so exit fast
+if [[ ${parts[0]} -eq 0 && ${parts[1]} -lt 18 ]] ; then
+    exit 0
+fi
+# If the source version is newer than the version under test exit fast because
+# there is no QPY compatibility for loading a qpy file generated from a newer
+# release with an older release of Qiskit.
+if [[ ${parts[0]} -gt ${qiskit_parts[0]} || ${parts[1]} -gt ${qiskit_parts[1]} ]] ; then
     exit 0
 fi