Fixes to mps_user_command():  - fix the leak of command struct on error  - simplify the cleanup logic  - EINPROGRESS is not a fatal error  - buggy comment and error message
Fixes to mps_user_command():
 - fix the leak of command struct on error
 - simplify the cleanup logic
 - EINPROGRESS is not a fatal error
 - buggy comment and error message

Reviewed by:   ken

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