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

tests/zfs-tests/cmd/draid.c

@@ -849,6 +849,7 @@ restart:
 			if (rc < 0) {
 				printf("Unable to read /dev/urandom: %s\n:",
 				    strerror(errno));
+				close(fd);
 				return (1);
 			}
 			bytes_read += rc;