ad8b4c1 dp: add dp_error_to_ret

Authored and Committed by pbrezina 4 years ago
    dp: add dp_error_to_ret
    
    To convert (ret, dp_error) pair to single errno_t value.
    
    Resolves:
    https://pagure.io/SSSD/sssd/issue/2607
    
    Reviewed-by: Tomáš Halman <thalman@redhat.com>