Variable Installments Total amount field validation

1. Navigate to loan account creation page
2. Choose the Loan product with Variable Installments enabled.
3. Click on Continue button and navigate to Review Installments Page

1. Verify is all the Installment loan amount are editable text field, except for the last installment.
2. On entering any value other than positive decimal, on click of validate or preview button, an error message should be thrown.