Neopallium server-side fixes and improvements

[emersion]

This is https://github.com/emersion/go-imap/pull/300 rebased against master.

The AutoLogout test has a race:

==================
WARNING: DATA RACE
Write at 0x00c000172800 by goroutine 51:
  github.com/emersion/go-imap/server_test.TestLogin_AutoLogout()
      /home/simon/src/go-imap/server/cmd_noauth_test.go:133 +0x134
  testing.tRunner()
      /usr/lib/go/src/testing/testing.go:909 +0x199

Previous read at 0x00c000172800 by goroutine 46:
  github.com/emersion/go-imap/server.(*conn).setDeadline()
      /home/simon/src/go-imap/server/conn.go:134 +0x6a
  github.com/emersion/go-imap/server.(*conn).greet()
      /home/simon/src/go-imap/server/conn.go:151 +0x3f7
  github.com/emersion/go-imap/server.(*conn).serve()
      /home/simon/src/go-imap/server/conn.go:285 +0x138
  github.com/emersion/go-imap/server.(*Server).serveConn()
      /home/simon/src/go-imap/server/server.go:289 +0x1c1

Goroutine 51 (running) created at:
  testing.(*T).Run()
      /usr/lib/go/src/testing/testing.go:960 +0x651
  testing.runTests.func1()
      /usr/lib/go/src/testing/testing.go:1202 +0xa6
  testing.tRunner()
      /usr/lib/go/src/testing/testing.go:909 +0x199
  testing.runTests()
      /usr/lib/go/src/testing/testing.go:1200 +0x521
  testing.(*M).Run()
      /usr/lib/go/src/testing/testing.go:1117 +0x2ff
  main.main()
      _testmain.go:198 +0x223

Goroutine 46 (running) created at:
  github.com/emersion/go-imap/server.(*Server).Serve()
      /home/simon/src/go-imap/server/server.go:237 +0x256
==================

Also, the AutoLogout test consistently takes 2 seconds. Not sure how to improve that since it's time-related.

cc @Neopallium

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@b27ce89). Click here to learn what that means. The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #338   +/-   ##
=========================================
  Coverage          ?   73.90%           
=========================================
  Files             ?       32           
  Lines             ?     3537           
  Branches          ?        0           
=========================================
  Hits              ?     2614           
  Misses            ?      633           
  Partials          ?      290           

Impacted Files	Coverage Δ
seqset.go	97.18% <0.00%> (ø)
client/cmd_any.go	57.89% <0.00%> (ø)
client/cmd_selected.go	73.60% <0.00%> (ø)
mailbox.go	82.40% <0.00%> (ø)
search.go	62.12% <0.00%> (ø)
utf7/utf7.go	100.00% <0.00%> (ø)
backend/backendutil/flags.go	100.00% <0.00%> (ø)
server/cmd_noauth.go	86.56% <0.00%> (ø)
server/cmd_selected.go	85.71% <0.00%> (ø)
command.go	60.00% <0.00%> (ø)
... and 22 more

---

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[foxcpp]

The AutoLogout test has a race:

testServer* functions need "server configuration" callbacks like it is done in go-smtp to set all necessary settings before connecting.

[emersion]

Closing because this is superseded by go-imap v2.