builder/powervs/common/ssh.go needs refactor

[mkumatag]

dhcp type network needs to be handled properly here in the code - https://github.com/mkumatag/packer-plugin-powervs/blob/41c31fb1fa6e1b0c236e1079729d1177ee2bca8a/builder/powervs/common/ssh.go#L50