netlink: Fix "or-fun-call" clippy warnings

The error shown below was caught during a dependency bump in the CCv0
branch, but we better fix it here first.
```
error: use of `ok_or` followed by a function call
   --> src/netlink.rs:526:14
    |
526 |             .ok_or(anyhow!(nix::Error::EINVAL))?;
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `ok_or_else(|| anyhow!(nix::Error::EINVAL))`
    |
    = note: `-D clippy::or-fun-call` implied by `-D warnings`
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#or_fun_call
error: use of `ok_or` followed by a function call
   --> src/netlink.rs:615:49
    |
615 |         let v = u8::from_str_radix(split.next().ok_or(anyhow!(nix::Error::EINVAL))?, 16)?;
    |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `ok_or_else(|| anyhow!(nix::Error::EINVAL))`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#or_fun_call
```

Fixes: #4523

Signed-off-by: Fabiano Fidêncio <fabiano.fidencio@intel.com>

src/agent/src/netlink.rs

@@ -523,7 +523,7 @@ impl Handle {
             .as_ref()
             .map(|to| to.address.as_str()) // Extract address field
             .and_then(|addr| if addr.is_empty() { None } else { Some(addr) }) // Make sure it's not empty
-            .ok_or(anyhow!(nix::Error::EINVAL))?;
+            .ok_or_else(|| anyhow!(nix::Error::EINVAL))?;
 
         let ip = IpAddr::from_str(ip_address)
             .map_err(|e| anyhow!("Failed to parse IP {}: {:?}", ip_address, e))?;
@@ -612,7 +612,7 @@ fn parse_mac_address(addr: &str) -> Result<[u8; 6]> {
 
     // Parse single Mac address block
     let mut parse_next = || -> Result<u8> {
-        let v = u8::from_str_radix(split.next().ok_or(anyhow!(nix::Error::EINVAL))?, 16)?;
+        let v = u8::from_str_radix(split.next().ok_or_else(|| anyhow!(nix::Error::EINVAL))?, 16)?;
         Ok(v)
     };