utils_disk: add function to retrieve partitions by disk path

On s390x, ccw disk order might change between boots.

`get_parts_list` therefore might return partitions on `vda` but
on `vdb` after reboot leading to unstable tests.

Add a new function `get_parts_list_by_path` which lists partitions
uniquely by their devno, e.g. `ccw-0.0.0009-part1`.

Signed-off-by: Sebastian Mitterle <[email protected]>

virttest/utils_disk.py

@@ -26,6 +26,7 @@
 
 from virttest import error_context
 from virttest import utils_numeric
+from virttest import utils_misc
 from virttest import remote
 
 PARTITION_TABLE_TYPE_MBR = "msdos"
@@ -1083,6 +1084,19 @@ def linux_disk_check(session, did):
         clean_partition_linux(session, did)
 
 
+def get_parts_list_by_path(session=None):
+    """
+    Get all partitions as listed on /dev/disk/by-path
+    """
+    err, out = utils_misc.cmd_status_output("ls /dev/disk/by-path",
+                                            shell=True, session=session)
+    if err:
+        raise exceptions.TestError("Failed to list partitions in /dev/disk/by-path")
+    r = out.split()
+    logging.debug("Partitions by path: %s", r)
+    return r
+
+
 def get_parts_list(session=None):
     """
     Get all partition lists.