server: use ecdsa instead of ed25519 when generate public/private keys (#8719)

PR #8549 replaced RSA with ed25519. unfornately, ed25519 is unsupported in FIPS mode

```
$  ssh-keygen -t ed25519 -m PEM -N '' -f key1
ED25519 keys are not allowed in FIPS mode

$  ssh-keygen -t ecdsa -m PEM -N '' -f key1
Generating public/private ecdsa key pair.
Your identification has been saved in key1
Your public key has been saved in key1.pub
The key fingerprint is:
.........

```

Author: weizhouapache

server/src/main/java/com/cloud/server/ConfigurationServerImpl.java

@@ -619,7 +619,7 @@ public void updateKeyPairs() {
             // FIXME: take a global database lock here for safety.
             boolean onWindows = isOnWindows();
             if(!onWindows) {
-                Script.runSimpleBashScript("if [ -f " + privkeyfile + " ]; then rm -f " + privkeyfile + "; fi; ssh-keygen -t ed25519 -m PEM -N '' -f " + privkeyfile + " -q 2>/dev/null || ssh-keygen -t ed25519 -N '' -f " + privkeyfile + " -q");
+                Script.runSimpleBashScript("if [ -f " + privkeyfile + " ]; then rm -f " + privkeyfile + "; fi; ssh-keygen -t ecdsa -m PEM -N '' -f " + privkeyfile + " -q 2>/dev/null || ssh-keygen -t ecdsa -N '' -f " + privkeyfile + " -q");
             }
 
             final String privateKey;