Disable nopwrite_volume and zpool_scrub tests

Disable these tests due to unrelated failures.  This patch should not
be merged as part of this PR and is only for testing purposes.

tests/runfiles/linux.run

@@ -327,9 +327,9 @@ tests = ['zpool_remove_001_neg', 'zpool_remove_002_pos']
 [tests/functional/cli_root/zpool_replace]
 tests = ['zpool_replace_001_neg']
 
-[tests/functional/cli_root/zpool_scrub]
-tests = ['zpool_scrub_001_neg', 'zpool_scrub_002_pos', 'zpool_scrub_003_pos',
-    'zpool_scrub_004_pos', 'zpool_scrub_005_pos']
+#[tests/functional/cli_root/zpool_scrub]
+#tests = ['zpool_scrub_001_neg', 'zpool_scrub_002_pos', 'zpool_scrub_003_pos',
+#    'zpool_scrub_004_pos', 'zpool_scrub_005_pos']
 
 [tests/functional/cli_root/zpool_set]
 tests = ['zpool_set_001_pos', 'zpool_set_002_neg', 'zpool_set_003_neg']
@@ -484,10 +484,10 @@ tests = ['enospc_001_pos']
 
 # DISABLED:
 # nopwrite_varying_compression - needs investigation
+# nopwrite_volume - occasionally hangs
 [tests/functional/nopwrite]
 tests = ['nopwrite_copies', 'nopwrite_mtime', 'nopwrite_negative',
-    'nopwrite_promoted_clone', 'nopwrite_recsize', 'nopwrite_sync',
-    'nopwrite_volume']
+    'nopwrite_promoted_clone', 'nopwrite_recsize', 'nopwrite_sync']
 
 # DISABLED: needs investigation
 #[tests/functional/online_offline]