ZTS: Fix and change testcase cache_010_neg

Commit 379ca9c removed the requirement on aux devices to be block
devices only but the test case cache_010_neg was not updated, making it
fail consistently.

This change changes the test to check that cache devices _can_ be
anything that presents a block interface. The testcase is renamed to
cache_010_pos and the exceptions for known failure removed from the test
runner.

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reported-by: Richard Elling <Richard.Elling@RichardElling.com>
Signed-off-by: Alex John <alex@stty.io>
Closes #10172

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

@@ -191,7 +191,6 @@ elif sys.platform.startswith('linux'):
 maybe = {
     'alloc_class/alloc_class_012_pos': ['FAIL', '9142'],
     'alloc_class/alloc_class_013_pos': ['FAIL', '9142'],
-    'cache/cache_010_neg': ['FAIL', known_reason],
     'chattr/setup': ['SKIP', exec_reason],
     'cli_root/zdb/zdb_006_pos': ['FAIL', known_reason],
     'cli_root/zfs_get/zfs_get_004_pos': ['FAIL', known_reason],