IpManagerTest: fix flaky test for real

Commit c10fe5f46367 tried to fix the flaky unit test for a default
ProvisioningConfiguration but failed to reinitialize the mock class
involved, so that in practice the flaky assertion is as flaky as before.

This patch correctly resets the mock after the default assertions are
done once an IpManager object is created.

Bug: 32561414
Bug: 62918393
Test: runtest frameworks-net
Change-Id: I516b6981f96e83a90cb372a727c41f0b2ea59801
diff --git a/tests/net/java/android/net/ip/IpManagerTest.java b/tests/net/java/android/net/ip/IpManagerTest.java
index 867324d..dc77e22 100644
--- a/tests/net/java/android/net/ip/IpManagerTest.java
+++ b/tests/net/java/android/net/ip/IpManagerTest.java
@@ -22,6 +22,7 @@
 import static org.mockito.Mockito.eq;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.timeout;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
@@ -93,6 +94,7 @@
         final IpManager ipm = new IpManager(mContext, ifname, mCb, mNMService);
         verify(mNMService, timeout(100).times(1)).disableIpv6(ifname);
         verify(mNMService, timeout(100).times(1)).clearInterfaceAddresses(ifname);
+        reset(mNMService);
         return ipm;
     }