Merge branch 'mysql-pvc' into 'master'

Add PVC support for MySQL

See merge request !28
2 jobs for master in 3 minutes and 19 seconds (queued for 2 seconds)
Name Stage Failure
failed
GoTest Go Test

Ran 1 of 0 Specs in 0.009 seconds
FAIL! -- 0 Passed | 1 Failed | 0 Pending | 0 Skipped
--- FAIL: TestAPIs (0.01s)
FAIL
FAIL gitlab.cern.ch/drupal/paas/drupalsite-operator/controllers 0.037s
FAIL
Cleaning up file based variables
ERROR: Job failed: exit code 1