flimflam: Fix set_apn issues.

This CL fixes set_apn to work on 64-bit platforms and be compatible with
shill.

BUG=chromium-os:33179
TEST=Tested the following commands with flimflam and shill:
1. set_apn
2. set_apn -c
3. set_apn -u <username> -p <password> <apn>
4. set_apn -n <network_id> -u <username> -p <password> <apn>

(cherry picked from commit 5cb0316cadc25287c5f0186ebe99eb8ee76c78ba)

Change-Id: Ie42baa822992fa67c6bdc699cad63143d594ed5b
Reviewed-on: https://gerrit.chromium.org/gerrit/29425
Reviewed-by: Ben Chan <[email protected]>
Tested-by: Ben Chan <[email protected]>
1 file changed