TestDiskUsage: don't panic if results don't match
This test is currently failing with containerd-integration, which should
be looked into, but let's start with preventing it from panicking, to make
the test-failures less noisy;
--- FAIL: TestDiskUsage/after_container.Run (0.26s)
panic: runtime error: index out of range [0] with length 0 [recovered]
panic: runtime error: index out of range [0] with length 0
goroutine 280 [running]:
testing.tRunner.func1.2({0xb07a00, 0x40002006a8})
/usr/local/go/src/testing/testing.go:1526 +0x1c8
testing.tRunner.func1()
/usr/local/go/src/testing/testing.go:1529 +0x364
panic({0xb07a00, 0x40002006a8})
/usr/local/go/src/runtime/panic.go:884 +0x1f4
github.com/docker/docker/integration/system.TestDiskUsage.func3(0x0?, {0x0, {0x14ea4a8, 0x0, 0x0}, {0x14ea4a8, 0x0, 0x0}, {0x14ea4a8, 0x0, ...}, ...})
/go/src/github.com/docker/docker/integration/system/disk_usage_test.go:82 +0x7e4
github.com/docker/docker/integration/system.TestDiskUsage.func4(0x4000235c80?)
/go/src/github.com/docker/docker/integration/system/disk_usage_test.go:118 +0x8c
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>