* virStorageEncryptionFormat is called from both
  virDomainDiskDefFormat and virStorageVolTargetDefFormat.  The proper
  indentation in the generated XML depends on the caller.  My earlier
  patch to fix the incorrect indentation for the domain XML broke the
  indentation for the storage XML.  This patch adopts Laine's
  suggestion of requring the caller of virStorageEncryptionFormat to
  provide an unsigned int with the number of spaces the output should
  be indented.  The patch modifies both callers to provide the
  additional argument.

* Add a regression test for the domain XML

* src/conf/domain_conf.c src/conf/storage_conf.c
  src/conf/storage_encryption_conf.c src/conf/storage_encryption_conf.h:
  change the indentation code
* tests/qemuxml2xmltest.c
  tests/qemuxml2argvdata/qemuxml2argv-encrypted-disk.args
  tests/qemuxml2argvdata/qemuxml2argv-encrypted-disk.xml: add a regression test