Refactor current patching code
Refactor current patching code

* Refactors the current patch code to allow for multiple patches that
  can be applied, yet leaves only one for now.

* Rewords the message shown to the user in case the modules needed for
  patching are missing.

Signed-off-by: Hrvoje Ribicic <be5828fca31f89218048bec4189e30a581aa65da@google.com>
Reviewed-by: Michele Tartara <05f7077a2c6cbbdc4af4ba42e3ef89a0df846179@google.com>

leshchevds/ganeti,apyrgio/snf-ganeti,leshchevds/ganeti,apyrgio/ganeti,mbakke/ganeti,dimara/ganeti,grnet/snf-ganeti,andir/ganeti,dimara/ganeti,mbakke/ganeti,onponomarev/ganeti,bitemyapp/ganeti,yiannist/ganeti,andir/ganeti,apyrgio/ganeti,yiannist/ganeti,onponomarev/ganeti,ganeti-github-testing/ganeti-test-1,apyrgio/snf-ganeti,grnet/snf-ganeti,ganeti/ganeti,andir/ganeti,ganeti-github-testing/ganeti-test-1,leshchevds/ganeti,ganeti/ganeti,mbakke/ganeti,yiannist/ganeti,bitemyapp/ganeti,ganeti/ganeti