Fix userland resource leaks

Coverity caught these. With the exception of the file descriptor leak in
tests/zfs-tests/cmd/draid.c, they are all memory leaks.

Also, there is a piece of dead code in zfs_get_enclosure_sysfs_path().
We delete it as cleanup.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #13921

cmd/zhack.c

@@ -295,6 +295,8 @@ zhack_do_feature_enable(int argc, char **argv)
 			feature.fi_flags |= ZFEATURE_FLAG_READONLY_COMPAT;
 			break;
 		case 'd':
+			if (desc != NULL)
+				free(desc);
 			desc = strdup(optarg);
 			break;
 		default: