TT#145801 billing.journals remove unique key txid_idx

* there can be more than one journal record created per a
  transaction (e.g. a subscriber and a customer are created
  at once, therefore the tx_id field cannot be unique)

Change-Id: I0046f41ec52412dbad319610d7b1b87988798586

db_scripts/diff/15707.down

@@ -0,0 +1,5 @@
+USE billing;
+
+ALTER TABLE billing.journals
+  DROP KEY txid_idx,
+   ADD UNIQUE KEY txid_idx (tx_id);

db_scripts/diff/15707.up

@@ -0,0 +1,5 @@
+USE billing;
+
+ALTER TABLE billing.journals
+  DROP KEY txid_idx,
+   ADD KEY txid_idx (tx_id);