Fix portage mod usage of jobs and load-average opt

In short, it enables portage module to emit emerge
command with --jobs and --load-average options
with and without argument.

To emit emerge with such CLI argument without
a value, the user must set the corresponding
module option to 0.

By default, if these arguments are missing from
playbook they are omitted.

Misc changes:

* Use to_native to ensure crosspython compat

* Adjust jobs and LA options to accept 0 as reset

* Add docstring to emerge_packages

* Explicitly note in doc that False will work as 0

PR  #36355 by @webknjaz

lib/ansible/modules/packaging/os/portage.py

@@ -156,6 +156,8 @@ options:
   jobs:
     description:
       - Specifies the number of packages to build simultaneously.
+      - "Since version 2.6: Value of 0 or False resets any previously added"
+      - --jobs setting values
     required: false
     default: None
     version_added: 2.3
@@ -164,6 +166,8 @@ options:
     description:
       - Specifies that no new builds should be started if there are
       - other builds running and the load average is at least LOAD
+      - "Since version 2.6: Value of 0 or False resets any previously added"
+      - --load-average setting values
     required: false
     default: None
     version_added: 2.3
@@ -224,6 +228,7 @@ import os
 import re
 
 from ansible.module_utils.basic import AnsibleModule
+from ansible.module_utils._text import to_native
 
 
 def query_package(module, package, action):
@@ -287,6 +292,7 @@ def sync_repositories(module, webrsync=False):
 
 
 def emerge_packages(module, packages):
+    """Run emerge command against given list of atoms."""
     p = module.params
 
     if not (p['update'] or p['noreplace'] or p['state'] == 'latest'):
@@ -326,13 +332,24 @@ def emerge_packages(module, packages):
         module.fail_json(msg='Use only one of usepkg, usepkgonly')
 
     emerge_flags = {
-        'jobs': '--jobs=',
-        'loadavg': '--load-average ',
+        'jobs': '--jobs',
+        'loadavg': '--load-average',
     }
 
     for flag, arg in emerge_flags.items():
-        if p[flag] is not None:
-            args.append(arg + str(p[flag]))
+        flag_val = p[flag]
+
+        if flag_val is None:
+            """Fallback to default: don't use this argument at all."""
+            continue
+
+        if not flag_val:
+            """If the value is 0 or 0.0: add the flag, but not the value."""
+            args.append(arg)
+            continue
+
+        """Add the --flag=value pair."""
+        args.extend((arg, to_native(flag_val)))
 
     cmd, (rc, out, err) = run_emerge(module, packages, *args)
     if rc != 0: