[Instrument_Status] Keep flag Required_elements_completed Up-to-date

[skarya22]

Brief summary of changes

• Update Instrument_Status to calculate and update the Required_elements_completed flag again on load / save
• CCNA has had a recurring issue where instruments could not be set to Data_entry = 'Complete' because Required_elements_completed was set to 'N' even though the elements were completed.

Testing instructions (if applicable)

1. Find a completed instrument
2. set Required_elements_completed = 'N'
3. Open the instrument and see that it was changed to 'Y'

[driusan]

Discussed in assignment meeting. This is happening because of code changes to the required elements on CCNA. The better solution is to write a script which calls this function when the code changes, rather than having side effects on load. @skarya22 to make changes.