Increase integration test timeout from 5m to 10m

Networking tests have been creeping towards the limit for a
while, but they're reliably failing in a upcoming PR that adds
a relatively slow test.

Signed-off-by: Rob Murray <rob.murray@docker.com>

hack/make/.integration-test-helpers

@@ -14,7 +14,7 @@ source "${MAKEDIR}/.go-autogen"
 
 # Set defaults
 : "${TEST_REPEAT:=1}"
-: "${TIMEOUT:=5m}"
+: "${TIMEOUT:=10m}"
 : "${TESTFLAGS:=}"
 : "${TESTDEBUG:=}"
 : "${TESTCOVERAGE:=}"