Fixed incorrect handling of re-creating network agent

1. When re-creating the network agent, the previous link
   properties needs to be filled.
2. Fixed the incorrect logic to detect immutable capabilities
   changed.

Fix: 217568288
Fix: 216855332
Test: atest DataNetworkTest
Change-Id: Ib938c050deafa834b2cd6e30de3e9560f2d72536
Merged-In: Ib938c050deafa834b2cd6e30de3e9560f2d72536