Added a copy assignment operator to `net::IP::Network`.
Added a copy assignment operator to `net::IP::Network`.

Review: https://reviews.apache.org/r/61004/

Gilbert88/mesos,verizonlabs/mesos,kaysoky/mesos,kaysoky/mesos,kaysoky/mesos,abudnik/mesos,abudnik/mesos,zmalik/mesos,Gilbert88/mesos,andschwa/mesos,jpeach/mesos,jpeach/mesos,verizonlabs/mesos,zmalik/mesos,jpeach/mesos,asamerh4/mesos,andschwa/mesos,dforsyth/mesos,verizonlabs/mesos,verizonlabs/mesos,kaysoky/mesos,abudnik/mesos,chhsia0/mesos,gsantovena/mesos,asamerh4/mesos,reneploetz/mesos,asamerh4/mesos,jpeach/mesos,verizonlabs/mesos,reneploetz/mesos,gsantovena/mesos,chhsia0/mesos,andschwa/mesos,gsantovena/mesos,abudnik/mesos,jpeach/mesos,reneploetz/mesos,dforsyth/mesos,Gilbert88/mesos,zmalik/mesos,andschwa/mesos,dforsyth/mesos,chhsia0/mesos,dforsyth/mesos,jpeach/mesos,asamerh4/mesos,Gilbert88/mesos,gsantovena/mesos,zmalik/mesos,gsantovena/mesos,zmalik/mesos,abudnik/mesos,asamerh4/mesos,abudnik/mesos,asamerh4/mesos,zmalik/mesos,andschwa/mesos,chhsia0/mesos,verizonlabs/mesos,reneploetz/mesos,verizonlabs/mesos,andschwa/mesos,zmalik/mesos,dforsyth/mesos,chhsia0/mesos,dforsyth/mesos,jpeach/mesos,reneploetz/mesos,kaysoky/mesos,asamerh4/mesos,reneploetz/mesos,kaysoky/mesos,chhsia0/mesos,dforsyth/mesos,gsantovena/mesos,andschwa/mesos,Gilbert88/mesos,abudnik/mesos,Gilbert88/mesos,reneploetz/mesos,gsantovena/mesos,kaysoky/mesos,Gilbert88/mesos,chhsia0/mesos