keygen: Update the cached vars after a keygen

This makes sure we can just re-use the same keystore without having to
reinitialize it.

Change-Id: I15e54030a54c0176dc755d8a6704bd51ae90104a
diff --git a/mdt/keys.py b/mdt/keys.py
index ea8f399..ce2c5e5 100644
--- a/mdt/keys.py
+++ b/mdt/keys.py
@@ -17,6 +17,9 @@
         self.private_key = self.config.getKey("mdt")
         self.public_key = self.config.getKey("mdt.pub")
 
+    def privateKeyPath(self):
+        return os.path.join(config.CONFIG_KEYSDIR, "mdt")
+
     def generateKey(self):
         if platform.system() not in SUPPORTED_SYSTEMS:
             print('Sorry, MDT doesn\'t support generating SSH keys on platforms other than:')
@@ -27,7 +30,7 @@
             subprocess.run([
                 "ssh-keygen",
                 "-f",
-                os.path.join(config.CONFIG_KEYSDIR, "mdt"),
+                self.privateKeyPath(),
                 "-P",
                 ""
             ], check=True)
@@ -39,6 +42,9 @@
             print('ssh-keygen failed with error code {0}'.format(e.returncode))
             return False
 
+        self.private_key = self.config.getKey("mdt")
+        self.public_key = self.config.getKey("mdt.pub")
+
         return True
 
     def publicKey(self):