fix: syncMetadata now takes into account that matched files can have a bucketPrefix

[JoaquinFernandez]

What has been implemented?

When bucketPrefix is specified in options, the files are correctly copied with the prefix in the s3 bucket. If you also specify metadata in params, then syncMetadata copies objects with the REPLACE directive with them, however, it does not take into account the bucketPrefix specified.

In order to overcome that I've added the bucketPrefix to the Key without a leading / and with an ending /

Closes #86 #57

Steps to verify

• Run serverless deploy command with bucketPrefix and without params

  • It should sync the files to the s3 bucket with the prefix and without tags

• Run serverless deploy command with bucketPrefix and with params

  • It should sync the files to the s3 bucket with the prefix and with tags and not duplicate on root folder. Further examples in https://github.com/k1LoW/serverless-s3-sync/issues/86 and https://github.com/k1LoW/serverless-s3-sync/issues/57

[k1LoW]

@JoaquinFernandez Thank you !!