It is not possible to use JDBC driver in JBPM in OSGI. 

KieBlueprintjBPMPersistenceKarafIntegrationTest.testStartProcessEnv fails with this error: Cannot load JDBC driver class 'com.mysql.cj.jdbc.Driver'
java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:418)

More detailed stack trace can be found in the stacktrace. https://qe-jenkins-csb-business-automation.apps.ocp-c1.prod.psi.redhat.com/job/TESTING/job/7.12/job/RHPAM-NIGHTLY/job/products_integration/job/certifications/job/community-tests-fuse-db-matrix/DATABASE=mysql80,FUSE_CONTAINER=GA,jdk=jdk1.8,label_exp=RHEL8/lastCompletedBuild/testReport/org.kie.karaf.itest.blueprint/KieBlueprintjBPMPersistenceKarafIntegrationTest/testStartProcessEnv/

Will work on reliable reproducer.