Added dedup of known_hosts

Cargo.lock

@@ -289,6 +289,12 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "either"
+version = "1.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fcaabb2fef8c910e7f4c7ce9f67a1283a1715879a7c230ca9d6d1ae31f16d91"
+
 [[package]]
 name = "encode_unicode"
 version = "0.3.6"
@@ -630,6 +636,15 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "itertools"
+version = "0.10.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.6"
@@ -1029,6 +1044,7 @@ dependencies = [
  "dialoguer",
  "dns-lookup",
  "env_logger",
+ "itertools",
  "lazy-st",
  "log",
  "massh",