ZTS: clean_mirror and scrub_mirror cleanup

Remove the dependency on partitionable devices for the clean_mirror
and scrub_mirror test cases.  This allows for the setup and cleanup
of the test cases to be simplified by removing the need for complex
partitioning.

This change also resolves a issue where the clean_mirror devices
were not being properly damaged since the device name was not a
full path.  The result being loopX files were being left in the
top level test_results directory.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #7434 
Closes #7690

tests/test-runner/bin/zts-report.py

@@ -202,7 +202,6 @@ maybe = {
     'cache/setup': ['SKIP', disk_reason],
     'cache/cache_010_neg': ['FAIL', known_reason],
     'chattr/setup': ['SKIP', exec_reason],
-    'clean_mirror/setup': ['SKIP', disk_reason],
     'cli_root/zdb/zdb_006_pos': ['FAIL', known_reason],
     'cli_root/zfs_get/zfs_get_004_pos': ['FAIL', known_reason],
     'cli_root/zfs_get/zfs_get_009_pos': ['SKIP', '5479'],
@@ -251,7 +250,6 @@ maybe = {
     'rsend/rsend_021_pos': ['FAIL', '6446'],
     'rsend/rsend_024_pos': ['FAIL', '5665'],
     'rsend/send-c_volume': ['FAIL', '6087'],
-    'scrub_mirror/setup': ['SKIP', disk_reason],
     'snapshot/clone_001_pos': ['FAIL', known_reason],
     'snapused/snapused_004_pos': ['FAIL', '5513'],
     'tmpfile/setup': ['SKIP', tmpfile_reason],