Add admin check before trying a remote wipe

* The code assumed that if we asked for a remote wipe, that it would
  be executed.  This isn't the case, however, if we're not a device
  admin at that time
* Test for Email app as device administrator before trying remote wipe

Bug: 2603931
Change-Id: I09dcff00e77bcf1e40c742c9dee923e6e07eecae

src/com/android/exchange/EasSyncService.java

@@ -1180,6 +1180,8 @@ public class EasSyncService extends AbstractSyncService {
             }
             if (pp.getRemoteWipe()) {
                 // We've gotten a remote wipe command
+                // If we're not the admin, we can't do the wipe, so just return
+                if (!sp.isActiveAdmin()) return false;
                 // First, we've got to acknowledge it, but wrap the wipe in try/catch so that
                 // we wipe the device regardless of any errors in acknowledgment
                 try {