[rilmodem] Gprs fake timer fixes

Fixes timer cancelation logic and a mem leak on timer
callback data cleanup.
[RILMODEM] fix sim mem leak and code cleaning

Signed-off-by: Jarko Poutiainen <Jarko.Poutiainen@oss.tieto.com>
Merge pull request #249 from jpoutiai/master

[RILMODEM] fix sim mem leak and code cleaning
Merge pull request #250 from tkenakka/gprs

[rilmodem] Gprs fake timer fixes