Update man page of gnt-instance
Update man page of gnt-instance

This patch updates the man page of gnt-instance to include the newly
added tags filtering.

Signed-off-by: René Nussbaumer <bc755ac45a0e799d1d490cba76febc56d80cc5fc@google.com>
Reviewed-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>
Reviewed-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>
Signed-off-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>

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