Use defined constant for consistency

[kenhys]

Which issue(s) this PR fixes:

Fixes #

What this PR does / why we need it:

The default value of dir or file permission is defined in fluent/env.rb.
So it should be used everywhere.

I've found this issue when checking #3521.

Docs Changes:

N/A

Release Note:

N/A

[ashie]

LGTM

storage_local.rb should also use them?

fluentd/lib/fluent/plugin/storage_local.rb

Lines 28 to 37 in da65272

	DEFAULT_DIR_MODE = 0755
	DEFAULT_FILE_MODE = 0644
	config_param :path, :string, default: nil
	config_param :mode, default: DEFAULT_FILE_MODE do |v|
	v.to_i(8)
	end
	config_param :dir_mode, default: DEFAULT_DIR_MODE do |v|
	v.to_i(8)
	end

[kenhys]

It should be, I'll fix it too.

[kenhys]

Fixed.

[kenhys]

Removed needless constant definition.