Refactor dhcp_utils for more flexible uses.

Separate out fetching DHCP results from starting the daemon
(for either discover or renew).

Renamed dhcp_do_request() to dhcp_start().
Renamed dhcp_do_request_renew() to dhcp_start_renew().
Added new dhcp_get_results().

Callers of the prior versions of dhcp_do_request* now separately
call dhcp_get_results().

Bug: 19422416
Change-Id: I05447853d444015e6014661dda1bb177b58fe463
diff --git a/include/netutils/dhcp.h b/include/netutils/dhcp.h
index de6bc82..008dbd8 100644
--- a/include/netutils/dhcp.h
+++ b/include/netutils/dhcp.h
@@ -23,26 +23,18 @@
 __BEGIN_DECLS
 
 extern int do_dhcp(char *iname);
-extern int dhcp_do_request(const char *ifname,
-                          char *ipaddr,
-                          char *gateway,
-                          uint32_t *prefixLength,
-                          char *dns[],
-                          char *server,
-                          uint32_t *lease,
-                          char *vendorInfo,
-                          char *domain,
-                          char *mtu);
-extern int dhcp_do_request_renew(const char *ifname,
-                                char *ipaddr,
-                                char *gateway,
-                                uint32_t *prefixLength,
-                                char *dns[],
-                                char *server,
-                                uint32_t *lease,
-                                char *vendorInfo,
-                                char *domain,
-                                char *mtu);
+extern int dhcp_start(const char *ifname);
+extern int dhcp_start_renew(const char *ifname);
+extern int dhcp_get_results(const char *ifname,
+                            char *ipaddr,
+                            char *gateway,
+                            uint32_t *prefixLength,
+                            char *dns[],
+                            char *server,
+                            uint32_t *lease,
+                            char *vendorInfo,
+                            char *domain,
+                            char *mtu);
 extern int dhcp_stop(const char *ifname);
 extern int dhcp_release_lease(const char *ifname);
 extern char *dhcp_get_errmsg();