nova flavor/keypair modification synced

we do the follow modification:
1. nova flavor/keypair modification synced;
2. sync the instance with certain states;
3. remove the unnecessary event record of cascading;
4. when glance sync image data, one suitable location woudl be
chosen.

Change-Id: I5981e2220a0f28b5b69e0b4fa887a096dc01109b