S3 Server error at existing a directory

[kmlebedev]

Describe the bug
S3 Server error at existing a directory

System Setup
version 30GB 2.04 linux amd64

Expected behavior

S3 api return status is file exist

Additional context
s3 client logs

Error executing "PutObject" on "https://s3-api/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip"; AWS HTTP error: Server error: `PUT https://s3-api/package-cache-repman/proxy/repo/dist/developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip` resulted in a `500 Internal Server Error` response:
<?xml version="1.0" encoding="UTF-8"?>
<Error><Code>InternalError</Code><Message>We encountered an internal error, pleas (truncated...)
 InternalError (server): We encountered an internal error, please try again. - <?xml version="1.0" encoding="UTF-8"?>
<Error><Code>InternalError</Code><Message>We encountered an internal error, please try again.</Message><Resource>/package-cache-repman/proxy/repo/dist/developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip</Resource><RequestId>1603184943256373611</RequestId></Error>

s3 and filer log

E1020 09:21:05     1 filer.go:239] existing /buckets/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip is a directory
E1020 09:21:05     1 filer.go:221] update entry /buckets/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip: existing /buckets/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip is a directory
I1020 09:21:05     1 filer_server_handlers_write_autochunk.go:184] failing to write /buckets/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip to filer server : update entry /buckets/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip: existing /buckets/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip is a directory
I1020 09:21:05     1 common.go:51] response method:PUT URL:/buckets/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip with httpStatus:500 and JSON:{"error":"update entry /buckets/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip: existing /buckets/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip is a directory"}
E1020 09:21:05     1 s3api_object_handlers.go:335] upload to filer error: update entry /buckets/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip: existing /buckets/package-cache-repman/proxy/repo/dist-developers/jsonrpc/9999999-dev_2478e8bfc36fb95ab7ce1afe7144e740b7b21a70.zip is a directory

[chrislusf]

Added a fix.