Enhance GET networks performance of metaplugin

Change to call plugin.get_networks() per target plugin
instead of calling plugin.get_network() per network.
Hook routines are used to select networks which belong
the target plugin.

Change-Id: Ieff06ac7bc7a150501f91aecc3197b0bb664d5fa
Closes-Bug: #1267290
Merge "Enhance GET networks performance of metaplugin"