Fix attribute get --with-comments for inline comments

[minamijoyo]

Follow-up to #103.

Inline comments belong to attributes, not expressions. When the --with-comments flag is specified, we need to return tokens on the right side of the equals sign.

$ cat tmp/iss102/main.tf
locals {
  map = {
    # comment
    attribute = "bar"
  }
  attribute = "foo" # comment
}

$ go run main.go attribute get -f tmp/iss102/main.tf locals.attribute
"foo"

$ go run main.go attribute get -f tmp/iss102/main.tf locals.attribute --with-comments
"foo" # comment

$ go run main.go attribute get -f tmp/iss102/main.tf locals.map
{

    attribute = "bar"
  }

[hcledit@fix-inline-comments|✔]$ go run main.go attribute get -f tmp/iss102/main.tf locals.map --with-comments
{
    # comment
    attribute = "bar"
  }