Merge branch 'mysql_insecure_password_warnings' into 'master'

Workaround the insecure password warnings emitted by MySQL 5.6

When using MySQL 5.6, the following output is emitted every time a backup is created, even with CRON=1.

```
Warning: Using a password on the command line interface can be insecure.
```

This fix works around that by sending the password via the [`MYSQL_PWD`](http://dev.mysql.com/doc/refman/5.6/en/environment-variables.html) environment variable.

See merge request !1139

lib/backup/database.rb

@@ -18,6 +18,8 @@ module Backup
       success = case config["adapter"]
       when /^mysql/ then
         $progress.print "Dumping MySQL database #{config['database']} ... "
+        # Workaround warnings from MySQL 5.6 about passwords on cmd line
+        ENV['MYSQL_PWD'] = config["password"].to_s if config["password"]
         system('mysqldump', *mysql_args, config['database'], out: db_file_name)
       when "postgresql" then
         $progress.print "Dumping PostgreSQL database #{config['database']} ... "
@@ -43,6 +45,8 @@ module Backup
       success = case config["adapter"]
       when /^mysql/ then
         $progress.print "Restoring MySQL database #{config['database']} ... "
+        # Workaround warnings from MySQL 5.6 about passwords on cmd line
+        ENV['MYSQL_PWD'] = config["password"].to_s if config["password"]
         system('mysql', *mysql_args, config['database'], in: db_file_name)
       when "postgresql" then
         $progress.print "Restoring PostgreSQL database #{config['database']} ... "
@@ -69,8 +73,7 @@ module Backup
         'port'      => '--port',
         'socket'    => '--socket',
         'username'  => '--user',
-        'encoding'  => '--default-character-set',
-        'password'  => '--password'
+        'encoding'  => '--default-character-set'
       }
       args.map { |opt, arg| "#{arg}=#{config[opt]}" if config[opt] }.compact
     end