Fixed missing open curly brace for nested hashes.

Before:

    if "nginx_error" in [type] {
        grok {
        'patterns_dir' => "/opt/logstash/server/etc/patterns"
            'add_field' =>                 'level' => "ERROR"
                'application_tag' => "nginx"
                }
            'match' =>                 'message' => ["%{POSINT:pid}#%{NUMBER}: %{GREEDYDATA:error_message}, client: %{IPORHOST:client}, server: %{DATA:request_server}, request: \"%{WORD:request_method} %{DATA:request_uri} HTTP/%{NUMBER:request_version:float}\"(?:, upstream: \"%{URI:upstream}\"|)(?:, host: \"(?:%{HOSTPORT:request_host}|%{IPORHOST:request_host}|))", "%{POSINT:pid}#%{NUMBER}: %{GREEDYDATA:error_message}"]

                }
        }
        alter {
            'coalesce' => ["message", "%{error_message}", "%{message}"]
        }
        mutate {
            'remove_field' => "error_message"
        }
   }

After:

    if "nginx_error" in [type] {
        grok {
        'patterns_dir' => "/opt/logstash/server/etc/patterns"
            'add_field' => {
                'level' => "ERROR"
                'application_tag' => "nginx"
            }
            'match' => {

                'message' => ["%{POSINT:pid}#%{NUMBER}: %{GREEDYDATA:error_message}, client: %{IPORHOST:client}, server: %{DATA:request_server}, request: \"%{WORD:request_method} %{DATA:request_uri} HTTP/%{NUMBER:request_version:float}\"(?:, upstream: \"%{URI:upstream}\"|)(?:, host: \"(?:%{HOSTPORT:request_host}|%{IPORHOST:request_host}|))", "%{POSINT:pid}#%{NUMBER}: %{GREEDYDATA:error_message}"]
            }
        }
        alter {
            'coalesce' => ["message", "%{error_message}", "%{message}"]
        }
        mutate {
            'remove_field' => "error_message"
        }
    }