test/lvm2: use LoopControl.loop_for_fd

Instead of having custom code that basically duplicates the
functionality of `LoopControl.loop_for_fd` use that instead.
Additionally, the version used in the test had a bug where
it did not re-create the Loop device in the main loop when
it was close due to an error, leading errors in subsequent
usages of the device that would often manifest in CI runs:
  fcntl.ioctl(self.fd, self.LOOP_SET_FD, fd)
  ValueError: file descriptor cannot be a negative integer (-1)

test/mod/test_util_lvm2.py

@@ -2,7 +2,6 @@
 # Test for the util.lvm2 module
 #
 
-import errno
 import os
 import json
 import subprocess
@@ -41,8 +40,6 @@ def tempdir_fixture():
 
 
 def make_loop(ctl, fd: int, offset, sizelimit, sector_size=512):
-    lo = loop.Loop(ctl.get_unbound())
-
     if not sizelimit:
         stat = os.fstat(fd)
         sizelimit = stat.st_size - offset
@@ -50,27 +47,7 @@ def make_loop(ctl, fd: int, offset, sizelimit, sector_size=512):
     else:
         sizelimit *= sector_size
 
-    while True:
-        try:
-            lo.set_fd(fd)
-        except OSError as e:
-            lo.close()
-            if e.errno == errno.EBUSY:
-                continue
-            raise e
-        # `set_status` returns EBUSY when the pages from the previously
-        # bound file have not been fully cleared yet.
-        try:
-            lo.set_status(offset=offset,
-                          sizelimit=sizelimit,
-                          autoclear=True)
-        except BlockingIOError:
-            lo.clear_fd()
-            lo.close()
-            continue
-        break
-
-    return lo
+    return ctl.loop_for_fd(fd, offset, sizelimit=sizelimit, autoclear=True)
 
 
 def pvcreate(path: PathLike):