Description of problem:
[graphical buffers]start guest failed when graphics defaultMode='secure', meanwhile add eight different channels mode='insecure'.

Version-Release number of selected component (if applicable):
libvirt-1.2.8-2.el7.x86_64
qemu-kvm-rhev-2.1.0-3.el7.x86_64
kernel-3.10.0-150.el7.x86_64


How reproducible:
100%

Steps to Reproduce:

1. Prepare a guest with the following content

#virsh dumpxml win7

<graphics type='spice' autoport='yes' listen='0.0.0.0' keymap='en-us' defaultMode='secure'>
      <listen type='address' address='0.0.0.0'/>
      <channel name='main' mode='insecure'/>
      <channel name='display' mode='insecure'/>
      <channel name='inputs' mode='insecure'/>
      <channel name='cursor' mode='insecure'/>
      <channel name='playback' mode='insecure'/>
      <channel name='record' mode='insecure'/>
      <channel name='smartcard' mode='insecure'/>
      <channel name='usbredir' mode='insecure'/>
    </graphics>
2. configure host to tls env for spice ssl connection,restart libvirtd service.

3. start the guest failed, there is an error reported.

## virsh start win7
error: Failed to start domain win7
error: internal error: process exited while connecting to monitor: 2014-09-18T05:18:28.616213Z qemu-kvm: spice: tried to setup tls-channel without specifying a TLS port

4.when delete any one of the channels, start guest again, it will be successful.

#virsh dumpxml win7

<graphics type='spice' autoport='yes' listen='0.0.0.0' keymap='en-us' defaultMode='secure'>
      <listen type='address' address='0.0.0.0'/>
      <channel name='main' mode='insecure'/>
      <channel name='inputs' mode='insecure'/>
      <channel name='cursor' mode='insecure'/>
      <channel name='playback' mode='insecure'/>
      <channel name='record' mode='insecure'/>
      <channel name='smartcard' mode='insecure'/>
      <channel name='usbredir' mode='insecure'/>
    </graphics>

# virsh start win7
Domain win7 started

5. the issue also hit on RHEL6.6

Actual results:
when configure graphics defaultMode='secure', meanwhile add eight different channel mode='insecure', start guest failed with error.


Expected results:
when configure graphics defaultMode='secure', meanwhile add eight different channel mode='insecure', start guest success.

Additional info:
reference the libvirt org about defaultMode:
The defaultMode attribute sets the default channel security policy, valid values are secure, insecure and the default any (which is secure if possible, but falls back to insecure rather than erroring out if no secure path is available). "defaultMode" since 0.9.12.
When SPICE has both a normal and TLS secured TCP port configured, it can be desirable to restrict what channels can be run on each port. This is achieved by adding one or more <channel> elements inside the main <graphics> element and setting the mode attribute to either secure or insecure. Setting the mode attribute overrides the default value as set by the defaultMode attribute. (Note that specifying any as mode discards the entry as the channel would inherit the default mode anyways) Valid channel names include main, display, inputs, cursor, playback, record (all since 0.8.6); smartcard (since 0.8.8); and usbredir (since 0.9.12).