remove empty if branch

[jeremyandrews]

• Fixes clippy detected issue:

error: this `if` branch is empty
Error:     --> src/metrics.rs:2549:9
     |
2549 |         if self.hosts.len() == 1 {}
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can remove it: `self.hosts.len() == 1;`
     |
     = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_if
     = note: `-D clippy::needless-if` implied by `-D warnings`

• Using git blame confirmed this was added during #342
• This slipped in during that earlier PR, and is not necessary; simply removing

[alecsmrekar]

Looks good!