Replace failing CoverityPublisher with plain 7zip and Curl
Replace failing CoverityPublisher with plain 7zip and Curl

Current build behavior is now:

 - Coverity analysis only happens on scheduled builds
 - Tests aren't run on scheduled builds
 - NuGet package generation only happens on merge commits
 - Coverity/NuGget publishing only happens on the last job of the matrix

jeffhostetler/public_libgit2sharp,rcorre/libgit2sharp,shana/libgit2sharp,OidaTiftla/libgit2sharp,whoisj/libgit2sharp,xoofx/libgit2sharp,vorou/libgit2sharp,AArnott/libgit2sharp,sushihangover/libgit2sharp,jorgeamado/libgit2sharp,psawey/libgit2sharp,Zoxive/libgit2sharp,AMSadek/libgit2sharp,sushihangover/libgit2sharp,AArnott/libgit2sharp,oliver-feng/libgit2sharp,xoofx/libgit2sharp,rcorre/libgit2sharp,psawey/libgit2sharp,libgit2/libgit2sharp,PKRoma/libgit2sharp,ethomson/libgit2sharp,whoisj/libgit2sharp,shana/libgit2sharp,Zoxive/libgit2sharp,vorou/libgit2sharp,Skybladev2/libgit2sharp,OidaTiftla/libgit2sharp,jorgeamado/libgit2sharp,Skybladev2/libgit2sharp,AMSadek/libgit2sharp,github/libgit2sharp,oliver-feng/libgit2sharp,github/libgit2sharp,red-gate/libgit2sharp,ethomson/libgit2sharp,red-gate/libgit2sharp,jeffhostetler/public_libgit2sharp,dlsteuer/libgit2sharp,dlsteuer/libgit2sharp