Fix gnt-node powercycle documentation
Fix gnt-node powercycle documentation

Fix options description in the documentation for gnt-node powercycle.

Signed-off-by: Luca Bigliardi <e702700dc9a886e6138bb50811fbdce0772e040e@google.com>
Reviewed-by: Guido Trotter <f62ca4d5358bdaeef0e50e57f9f7e231de63727e@google.com>

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