Snap

Fix locking in mgw::DisplayClient() #2857

Job	Run time
mir-libs (amd64)	19m 42s
mir-libs (armhf)	49m 43s
mir-libs (arm64)	53m 36s
snap (MirServer/mir-test-tools, amd64)	10m 58s
snap (MirServer/mir-test-tools, armhf)	26m 1s
snap (MirServer/mir-test-tools, arm64)	28m 34s
snap (MirServer/confined-shell-wip, amd64)	7m 4s
snap (MirServer/confined-shell-wip, armhf)	16m 4s
snap (MirServer/confined-shell-wip, arm64)	21m 37s
snap (MirServer/ubuntu-frame, amd64)	5m 6s
snap (MirServer/ubuntu-frame, armhf)	10m 17s
snap (MirServer/ubuntu-frame, arm64)	11m 43s
snap (Miriway/Miriway, amd64)	13m 8s
snap (Miriway/Miriway, armhf)	14m 16s
snap (Miriway/Miriway, arm64)	18m 25s
	5h 6m 14s

Provide feedback