Merge pull request #3594 from poettering/resolved-servfail

resolved fixes for handling SERVFAIL errors from servers

diff --cc src/resolve/resolved-dns-cache.c
Simple merge

diff --cc src/resolve/resolved-dns-server.c
Simple merge

diff --cc src/resolve/resolved-dns-server.h
Simple merge

diff --cc src/resolve/resolved-dns-transaction.c
Simple merge

diff --cc src/resolve/resolved-dns-transaction.h
Simple merge