[rilmodem] Set service class to 0 in call waiting query

Set service class to 0 in call waiting query as certain
operators can reject the query with specific service class

Signed-off-by: Petri Takalokastari <petri.takalokastari@oss.tieto.com>
Merge pull request #80 from ptakalok/master

[rilmodem] Set service class to 0 in call waiting query
Merge pull request #81 from jpoutiai/master

rilmodem: cancel USSD + minor style fix
gril:fix queue removing in cancel group + style fixes

Signed-off-by: Jarko Poutiainen <Jarko.Poutiainen@oss.tieto.com>