in_tail: Add a warning message on retrying to open an unaccecible file

When a fluentd proccess doesn't have permision to read a file, it should
retries to open it with a warning message. But the current
implementation suppresses the message due to #3378.
This patch revive the warning message.

Signed-off-by: Takuro Ashie <ashie@clear-code.com>

lib/fluent/plugin/in_tail.rb

@@ -1063,7 +1063,10 @@ def open
         rescue RangeError
           io.close if io
           raise WatcherSetupError, "seek error with #{@path}: file position = #{@watcher.pe.read_pos.to_s(16)}, reading bytesize = #{@fifo.bytesize.to_s(16)}"
-        rescue Errno::ENOENT, Errno::EACCES
+        rescue Errno::EACCES => e
+          @log.warn "#{e}"
+          nil
+        rescue Errno::ENOENT
           nil
         end