tests: don't use "losetup --find"

It slowed down firecracker-containerd's tests before.

Signed-off-by: Kazuyoshi Kato <[email protected]>

Author: kzys

tests/integration_tests/functional/test_drives.py

@@ -4,7 +4,7 @@
 
 import os
 import platform
-from subprocess import run, PIPE
+from subprocess import run
 
 import pytest
 
@@ -92,9 +92,11 @@ def test_rescan_dev(test_microvm_with_ssh, network_config):
         size=512
     )
 
-    losetup = ['losetup', '--find', '--show', fs2.path]
-    losetup_result = run(losetup, stdout=PIPE, check=True)
-    loopback_device = losetup_result.stdout.decode('utf-8').rstrip()
+    # "losetup --find" may slow down tests due to
+    # https://github.com/firecracker-microvm/firecracker-containerd/issues/141
+    loopback_device = f'/dev/loop{os.getpid()}'
+    losetup = ['losetup', loopback_device, fs2.path]
+    run(losetup, check=True)
 
     try:
         response = test_microvm.drive.patch(