Use rdroidtest attribute for loopdevice test cases

To make sure loopdevice tests are run properly in libdm_rust.test

Bug: None
Test: atest libdm_rust.test and observed loopdevice tests run

Change-Id: I572a9a33401fb72889dcaf1fd9ecba7effd00abc
diff --git a/libs/devicemapper/src/loopdevice.rs b/libs/devicemapper/src/loopdevice.rs
index 113a946..130c1c4 100644
--- a/libs/devicemapper/src/loopdevice.rs
+++ b/libs/devicemapper/src/loopdevice.rs
@@ -159,6 +159,7 @@
 #[cfg(test)]
 mod tests {
     use super::*;
+    use rdroidtest::rdroidtest;
     use std::fs;
     use std::path::Path;
 
@@ -178,7 +179,7 @@
         "0" == fs::read_to_string(ro).unwrap().trim()
     }
 
-    #[test]
+    #[rdroidtest]
     fn attach_loop_device_with_dio() {
         let a_dir = tempfile::TempDir::new().unwrap();
         let a_file = a_dir.path().join("test");
@@ -191,7 +192,7 @@
         assert!(is_direct_io(&dev));
     }
 
-    #[test]
+    #[rdroidtest]
     fn attach_loop_device_without_dio() {
         let a_dir = tempfile::TempDir::new().unwrap();
         let a_file = a_dir.path().join("test");
@@ -204,7 +205,7 @@
         assert!(!is_direct_io(&dev));
     }
 
-    #[test]
+    #[rdroidtest]
     fn attach_loop_device_with_dio_writable() {
         let a_dir = tempfile::TempDir::new().unwrap();
         let a_file = a_dir.path().join("test");