Bump coreos/etcd to v3.3.9 and go-systemd to v17

[vdemeester]

cc @chungers @mefyl

Signed-off-by: Vincent Demeester vincent@sbr.pm

[thaJeztah]

LGTM (if green)

this will conflict with #2718, which also bumps go-systemd

[thaJeztah]

TestNodeAllocator is a flaky test #2479 (and
#2700 (review))

time="2018-07-27T09:55:48Z" level=error msg="task allocation failure" error="failed to retrieve network testID3 while allocating task testTaskID3"
time="2018-07-27T09:55:49Z" 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="2018-07-27T09:55:49Z" level=error msg="task allocation failure" error="network testID5 attached to task testTaskID6 not allocated yet"
time="2018-07-27T09:55:49Z" level=error msg="Failed allocation for service testServiceID4" error="requested bit is already allocated"
time="2018-07-27T09:55:49Z" level=error msg="task allocation failure" error="service testServiceID4 to which task testTaskID7 belongs has pending allocations"
--- FAIL: TestNodeAllocator (0.01s)
	allocator_test.go:1427: timed out before watchNode found expected node state
FAIL

[cpuguy83]

This probably needs to upgrade testing as well as mixed-version testing as well.