Update unit tests

Author: Adrian Cruceru

mbedtls/src/ssl/config.rs

@@ -138,7 +138,7 @@ impl Drop for NullTerminatedStrList {
         for i in self.c.iter() {
             unsafe {
                 if !(*i).is_null() {
-                    ::std::ffi::CString::from_raw(*i);
+                    let _ = ::std::ffi::CString::from_raw(*i);
                 }
             }
         }

mbedtls/tests/ssl_conf_ca_cb.rs

@@ -60,7 +60,8 @@ mod test {
     use crate::support::keys;
     use mbedtls::x509::{Certificate};
     use mbedtls::Error;
-
+    use mbedtls::alloc::{List as MbedtlsList, Box as MbedtlsBox};
+    
     // This callback should accept any valid self-signed certificate
     fn self_signed_ca_callback(child: &MbedtlsList<Certificate>) -> TlsResult<MbedtlsList<Certificate>> {
         Ok(child.clone())