Add support for supplicant SCAN_INTERVAL

Also, allow scan interval for framework and supplicant
to be configured at build time or run time

Bug: 4144882
Change-Id: I877f4bcc872597b44d3f4da85cf2bc0f16e09444
diff --git a/services/java/com/android/server/WifiService.java b/services/java/com/android/server/WifiService.java
index 915b679..a2d10df 100644
--- a/services/java/com/android/server/WifiService.java
+++ b/services/java/com/android/server/WifiService.java
@@ -937,7 +937,7 @@
                 evaluateTrafficStatsPolling();
                 mWifiStateMachine.enableRssiPolling(true);
                 if (mBackgroundScanSupported) {
-                    mWifiStateMachine.enableBackgroundScan(false);
+                    mWifiStateMachine.enableBackgroundScanCommand(false);
                 }
                 mWifiStateMachine.enableAllNetworks();
                 updateWifiState();
@@ -949,7 +949,7 @@
                 evaluateTrafficStatsPolling();
                 mWifiStateMachine.enableRssiPolling(false);
                 if (mBackgroundScanSupported) {
-                    mWifiStateMachine.enableBackgroundScan(true);
+                    mWifiStateMachine.enableBackgroundScanCommand(true);
                 }
                 /*
                  * Set a timer to put Wi-Fi to sleep, but only if the screen is off