Don't delete certs. on account creation, & assure that only one instance of LocalKeyStore is created.

src/com/fsck/k9/Account.java

@@ -1900,6 +1900,10 @@ public class Account implements BaseAccount {
         }
         String oldHost = uri.getHost();
         int oldPort = uri.getPort();
+        if (oldPort == -1) {
+            // This occurs when a new account is created
+            return;
+        }
         if (!newHost.equals(oldHost) || newPort != oldPort) {
             LocalKeyStore localKeyStore = LocalKeyStore.getInstance(context);
             localKeyStore.deleteCertificate(oldHost, oldPort);

src/com/fsck/k9/security/LocalKeyStore.java

@@ -24,7 +24,7 @@ public class LocalKeyStore {
     private static LocalKeyStore sInstance;
 
 
-    public static LocalKeyStore getInstance(Context context) {
+    public synchronized static LocalKeyStore getInstance(Context context) {
         if (sInstance == null) {
             sInstance = new LocalKeyStore(context);
         }