Fix import from server

Was broken since 7bbe869c88c445b087e32a75572cf18efa2165b6
This also keeps the ACTION_IMPORT_KEYRING action stable
Undo import changes
Fix CachedPublicKeyring

I had this code already in my git, but it was in between the load of other things in there, just pulled it out.
Merge pull request #727 from mar-v-in/fix-cachedpublickeyring

Fix CachedPublicKeyring
Merge pull request #726 from mar-v-in/fix-import-from-server

Fix import from server
identity instead of credentials
Merge branch 'master' of github.com:open-keychain/open-keychain
Remve cacheing of keyrings (cleanup of #726)