fix(panos_software): Modify valid sequence for downloads only (#463)

plugins/modules/panos_software.py

@@ -33,6 +33,11 @@
 notes:
     - Panorama is supported.
     - Check mode is supported.
+    - When installing PAN-OS software, checking is performed by this module to
+      ensure the upgrade/downgrade path is valid. When using this module to only
+      download and not install PAN-OS software, the valid upgrade/downgrade path
+      checking is bypassed (in order to allow pre-downloading of PAN-OS software
+      images ahead of the installation time for multiple stage upgrades/downgrades).
 extends_documentation_fragment:
     - paloaltonetworks.panos.fragments.transitional_provider
 options:
@@ -211,7 +216,7 @@ def main():
             device.software.check()
 
         if target != current:
-            if not is_valid_sequence(current, target):
+            if not is_valid_sequence(current, target) and install:
                 module.fail_json(
                     msg="Version Sequence is invalid: {0} -> {1}".format(
                         current, target