gdhcp: Don't try to remove timer again

gdhcp: Don't try to remove timer again

GLib-CRITICAL warning message is obtained in below scenario:
1. service is connected and link local address is obtained.
2. Try to disconnect service.

(connmand:8377): GLib-CRITICAL **: Source ID 289 was not found when
attempting to remove it

(connmand:8377): GLib-CRITICAL **: Source ID 303 was not found when
attempting to remove it

When Link Local IP address is obtained then both dhcp_client->timeout
assigned for DISCOVER_TIMEOUT and ANNOUNCE_INTERVAL are already removed
when discover_timeout() and ipv4ll_announce_timeout() function returns
FALSE but the dhcp_client->timeout is not assigned to 0. Now when
dhcp_release() calls remove_timeouts() function then dhcp_client->timeout
is tried to remove again resulting in GLib-CRITICAL warning. This patch
removes all possible remaing timeouts in g_dhcp_client_start() and
explicitly sets dhcp_client->timeout to 0 in ipv4ll_announce_timeout()
function.

Change-Id: I12b072beef92818a2c1db253c85d1cfea540682b
Signed-off-by: Saurav Babu <saurav.babu@samsung.com>