backport ConstraintEnforcer fix

Revendors docker/swarmkit to backport fixes made to the
ConstraintEnforcer (see moby/swarmkit#2857)

Signed-off-by: Drew Erny <[email protected]>

Author: dperny

vendor.conf

@@ -130,7 +130,7 @@ github.com/containerd/ttrpc                         f02858b1457c5ca3aaec3a0803eb
 github.com/gogo/googleapis                          d31c731455cb061f42baff3bda55bad0118b126b # v1.2.0
 
 # cluster
-github.com/docker/swarmkit                          59163bf75df38489d4a10392265d27156dc473c5
+github.com/docker/swarmkit                          48eb1828ce81be20b25d647f6ca8f33d599f705c
 github.com/gogo/protobuf                            ba06b47c162d49f2af050fb4c75bcbc86a159d5c # v1.2.1
 github.com/cloudflare/cfssl                         5d63dbd981b5c408effbb58c442d54761ff94fbd # 1.3.2
 github.com/fernet/fernet-go                         1b2437bc582b3cfbb341ee5a29f8ef5b42912ff2