QMP/qemu-ga-client: Make timeout longer for guest-fsfreeze-freeze command

guest-fsfreeze-freeze command can take longer than 3 seconds when heavy
disk I/O is running. To avoid unexpected timeout, this changes the timeout
to 60 seconds (timeout of pre-commit phase of VSS).

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
