Replace deprecated Maven Surefire option forkMode with forkCount reuseForks

Maven indicates forkMode is deprecate and needs to be replaced with forkCount & reuseForks.

[WARNING] The parameter forkMode is deprecated since version 2.14. Use forkCount and reuseForks instead.

Exact mapping of the values can be found on: 

https://maven.apache.org/surefire/maven-surefire-plugin/examples/fork-options-and-parallel-execution.html

Grep results for forkMode:

./enterprise/reporting-dashboard/frontend/pom.xml:          <forkMode>always</forkMode>

./enterprise/targeting/frontend/pom.xml:          <forkMode>always</forkMode>

./enterprise/targeting/frontend-api/pom.xml:          <forkMode>always</forkMode>

./community/repository/deprecated/facetsearch/pom.xml:            <!-<forkMode>once</forkMode>->

./community/repository/deprecated/facetselectmirror/pom.xml:            <!-<forkMode>once</forkMode>->

./community/commons/pom.xml:          <forkMode>always</forkMode>