[18.03] Fix linting issues

[thaJeztah]

cherry-pick of #2693 for 18.03 branch

cherry-pick was clean; no conflicts

Go 1.11 is stricter, and compilation will fail, revealing these issues;

agent/agent_test.go:120: *github.com/docker/swarmkit/api.WeightedPeer composite literal uses unkeyed fields
agent/agent_test.go:125: *github.com/docker/swarmkit/api.WeightedPeer composite literal uses unkeyed fields
agent/agent_test.go:130: *github.com/docker/swarmkit/api.WeightedPeer composite literal uses unkeyed fields
agent/agent_test.go:135: *github.com/docker/swarmkit/api.WeightedPeer composite literal uses unkeyed fields
agent/agent_test.go:140: *github.com/docker/swarmkit/api.WeightedPeer composite literal uses unkeyed fields
manager/dispatcher/dispatcher.go:426: Entry.Info call has possible formatting directive %s
manager/dispatcher/dispatcher.go:547: Entry.Debug call has possible formatting directive %s
make: *** [vet] Error 1

Signed-off-by: Sebastiaan van Stijn github@gone.nl
(cherry picked from commit 59064c3)
Signed-off-by: Sebastiaan van Stijn github@gone.nl

- What I did

- How I did it

- How to test it

- Description for the changelog

[dperny]

LGTM

[thaJeztah]

Boo!

ok  	github.com/docker/swarmkit/manager	6.710s	coverage: 81.7% of statements
time="2018-07-09T23:03:36Z" level=error msg="task allocation failure" error="failed to retrieve network testID3 while allocating task testTaskID3" 
time="2018-07-09T23:03:36Z" level=error msg="Failed allocation for network testID5" error="failed while allocating driver state for network testID5: could not obtain vxlan id for pool 10.0.4.0/24: requested bit is already allocated" 
time="2018-07-09T23:03:36Z" level=error msg="task allocation failure" error="network testID5 attached to task testTaskID6 not allocated yet" 
time="2018-07-09T23:03:36Z" level=error msg="Failed allocation for service testServiceID4" error="requested bit is already allocated" 
time="2018-07-09T23:03:36Z" level=error msg="task allocation failure" error="service testServiceID4 to which task testTaskID7 belongs has pending allocations" 
--- FAIL: TestNodeAllocator (0.04s)
	allocator_test.go:1434: timed out before watchNode found expected node state
FAIL

[thaJeztah]

Tried to force push to trigger CI, and got the same failure, however, doing a "dummy" PR against the 18.03 branch doesn't show that failure; #2701

Is something flaky in this test, or can it be triggered somehow by the changes here?

[cyli]

LGTM - thanks @thaJeztah - TestNodeAllocator is known flakey.

[codecov]

Codecov Report

Merging #2700 into bump_v18.03 will decrease coverage by 0.32%.
The diff coverage is 50%.

@@               Coverage Diff               @@
##           bump_v18.03    #2700      +/-   ##
===============================================
- Coverage        61.82%   61.49%   -0.33%     
===============================================
  Files              134      134              
  Lines            21820    21820              
===============================================
- Hits             13491    13419      -72     
- Misses            6888     6948      +60     
- Partials          1441     1453      +12