MM-10020: avoid duplicating unique indexes (#8587)

* unit test TestGet(Search)Replica

This adds partial, testing-focused support for SQLite, as well as removing
some translated log messages that required initializing i18n just for
testing.

* avoid returning master twice when no replicas are configured

* remove duplicate indexes

* unit test GetAllConns

vendor/github.com/mattn/go-sqlite3/sqlite3_libsqlite3.go

@@ -0,0 +1,15 @@
+// Copyright (C) 2014 Yasuhiro Matsumoto <mattn.jp@gmail.com>.
+//
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+// +build libsqlite3
+
+package sqlite3
+
+/*
+#cgo CFLAGS: -DUSE_LIBSQLITE3
+#cgo linux LDFLAGS: -lsqlite3
+#cgo darwin LDFLAGS: -L/usr/local/opt/sqlite/lib -lsqlite3
+#cgo solaris LDFLAGS: -lsqlite3
+*/
+import "C"