Fix bug where nothing ever rotates

[JonasKop]

Fixes this bug: #11

The bug was caused since the stored terraform state timestamp was used to check whenever a rotation should happen. Since that value was always in the past, behind the expiration date a rotation was never performed. When using the current timestamp it now always works for me. I have tested it using the following terraform code with a .terraformrc dev override.

terraform {
  required_providers {
    multirotate = {
      source = "hashicorp.com/edu/multirotate"
    }
  }
}

resource "multirotate_set" "token_rotation" {
  rotation_period = "10s"
  number          = 2
}

resource "local_file" "example" {
  count    = multirotate_set.token_rotation.number
  filename = "file1-${count.index}"
  content  = multirotate_set.token_rotation.rotation_set[count.index].expiration
}

provider_installation {
  dev_overrides {
    "hashicorp.com/edu/multirotate" = "<MY_HOME_DIR>/go/bin"
  }
  direct {}
}

Closes #11