Auto generated keypair file name on windows include .\ which is invalid format

[kapilchouhan99]

Scenario:

Whenever the user doesn't provide ssh_key_name, The packer Amazon AMI builder will generate a temporary keypair. The generated keypair file name should be the correct format.

Steps to Reproduce:

If the user is provisioning a Windows host:

knife ec2 server create -N chef-node-name -I ami-0d639a48468c98db8 -f t2.micro -x '.\kpl-w' -P 'ec2user@123' --winrm-ssl --winrm-no-verify-cert --security-group-id sg-001bbf0c658b11a3b -VV -c /home/.chef/knife.rb

then Generated keypair file name like this: .\kpl-w-00051f26c438dc0fe2db.pem which is invalid format

Expected Result:

If the user is provisioning a Windows host, then Generated keypair file name should be like this: kpl-w-00051f26c438dc0fe2db.pem