Fix Azure ARM create_node JSON error with ex_customdata (#1893)

[Sanjays2402]

Description

Fixes #1893.

For the Azure ARM driver, create_node failed when ex_customdata was provided:

• base64.b64encode() returns bytes, which is not JSON serializable, so building the request body raised Object of type bytes is not JSON serializable.
• Passing ex_customdata as a str also failed because b64encode requires bytes-like input.

The fix normalizes ex_customdata to bytes, then decodes the base64 result to a UTF-8 str so customData is JSON-serializable. Both str and bytes inputs are now accepted.

Status

• done, ready for review

Checklist (tick everything that applies)

• Code linting (required, can be done after the PR checks) — black --check and flake8 clean on changed files
• Documentation
• Tests — added test_create_node_ex_customdata (str + bytes); fails without the fix, passes with it; full test_azure_arm.py = 46 passed
• ICLA (required for bigger changes) — small bugfix

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.39%. Comparing base (fbbfd08) to head (d74c50e).

Additional details and impacted files

@@            Coverage Diff             @@
##            trunk    #2159      +/-   ##
==========================================
+ Coverage   83.38%   83.39%   +0.01%     
==========================================
  Files         351      351              
  Lines       81457    81476      +19     
  Branches     8745     8746       +1     
==========================================
+ Hits        67919    67940      +21     
+ Misses      10745    10744       -1     
+ Partials     2793     2792       -1     

Files with missing lines	Coverage Δ
libcloud/compute/drivers/azure_arm.py	60.73% <100.00%> (+0.39%)	⬆️
libcloud/test/compute/test_azure_arm.py	99.01% <100.00%> (+0.03%)	⬆️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[micafer]

LGTM