[clinical] Some NLST dictionaries are not parsed correctly

[fedorov]

Specifically, see nlst_ctab sct_ab_desc column. Looks like "=" is used as a separator, and it is not considered that "=" may be encountered more than once.

This is what it is in the dictionary rtf:

Our table has this instead

SELECT
  *
FROM
  `bigquery-public-data.idc_current_clinical.column_metadata`
WHERE
  collection_id = "nlst"
  AND `column`="sct_ab_desc"

[fedorov]

It looks like the bug is here:

etl_flow/clinical/parse_clinical_files.py

Lines 932 to 934 in 96c30b2

	vals = ws.cell(row=row_ind, column=4).value.split('=')
	option_code = vals[0].strip('"').strip("'")
	option_description = vals[1].strip('"').strip("'")

Instead of split(), it should find first occurrence and split only once.