Bug 916719 - B2G Emulator: Fix bug in amodem_clear_call

Free calls in reverse order.
Merge pull request #47 from aknow/fix_gsm_clear

Bug 916719 - B2G Emulator: Fix bug in amodem_clear_call. r=vicamo
Merge remote-tracking branch 'b2g/master' into b2g-jellybean