tools : Update format of SpiceSecureChannels to "channel" from "schannel"

Update format of SpiceSecureChannels to "channel" from "schannel".
"schannel" (like smain, sinputs etc) is a leftover from qspice 0.3.x
from RHEL 5 days, since at least spice 0.6 (maybe even 0.4 from
RHEL 6.0), the format is changed to "channel" (main, inputs etc).

Change-Id: I87d4d3ee58e7730cc8243b313a220f49621e195a
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=803666
Signed-off-by: Ravi Nori <rnori@redhat.com>