Check if we have root access

Hostapd fails without root access.

Change-Id: Ib7211685795c3a1d5de64c014a0b28a71f2fe9fa
Reviewed-on: https://weave-review.googlesource.com/1430
Reviewed-by: Johan Euphrosine <proppy@google.com>

libweave/examples/provider/wifi_manager.cc

diff --git a/libweave/examples/provider/wifi_manager.cc b/libweave/examples/provider/wifi_manager.cc
index ac1c604..c70aad4 100644
--- a/libweave/examples/provider/wifi_manager.cc
+++ b/libweave/examples/provider/wifi_manager.cc
@@ -41,6 +41,8 @@
 
 WifiImpl::WifiImpl(provider::TaskRunner* task_runner, bool force_bootstrapping)
     : force_bootstrapping_{force_bootstrapping}, task_runner_{task_runner} {
+  CHECK_EQ(0, getuid())
+      << "WiFi manager expects root access to control WiFi capabilities";
   StopAccessPoint();
 }
 WifiImpl::~WifiImpl() {