fix: remove redundant variable initialization flagged by CodeQL

Removed dead store of rc variable in mgr_snapshot_cmd(). The variable
was initialized to SnapshotStatus.SNAPSHOT_OK but immediately overwritten
by verify_snapset_source_lvs_exist() before ever being used.

In the check_mode path, explicitly use SnapshotStatus.SNAPSHOT_OK instead
of the rc variable for clarity, since we know rc must be SNAPSHOT_OK at
that point (or we would have returned early on line 213-214).

This fixes CodeQL alert py/multiple-definition:
  'This assignment to rc is unnecessary as it is redefined before this
  value is used.'

Addresses: https://github.com/linux-system-roles/snapshot/security/code-scanning/95
Signed-off-by: Todd Gill <tgill@redhat.com>

Author: trgill

module_utils/snapshot_lsr/snapmgr.py

@@ -206,7 +206,6 @@ def mgr_snapshot_cmd(module, module_args, snapset_json):
     logger.info("mgr_snapshot_cmd: %s", snapset_name)
     changed = False
     message = ""
-    rc = SnapshotStatus.SNAPSHOT_OK
     check_mode = module_args["ansible_check_mode"]
 
     rc, message = verify_snapset_source_lvs_exist(module, snapset_json)
@@ -242,7 +241,7 @@ def mgr_snapshot_cmd(module, module_args, snapset_json):
 
     if check_mode:
         return {
-            "return_code": rc,
+            "return_code": SnapshotStatus.SNAPSHOT_OK,
             "errors": "Would call function manager.create_snapshot_set()",
             "changed": False,
         }