Test: wait for 5 minutes for Jenkins to start

The corresponding test is slightly flaky because sometime Jenkins
take a long time to start.

Change-Id: I8111ad034ed5a0215576ed4920b4b5e93a2ae25c
diff --git a/jenkins/test/common.sh b/jenkins/test/common.sh
index 2fa3843..41ae13c 100755
--- a/jenkins/test/common.sh
+++ b/jenkins/test/common.sh
@@ -53,7 +53,7 @@
 wait_for_server() {
   local server="${1:-localhost}"
   local port="${2:-8080}"
-  local timeout=180
+  local timeout=300
   local ts="$(date +%s)"
   echo -n "*** Waiting for jenkins server to be up and running on port ${port}"
   while ! [[ "$(curl -sI  "http://${server}:${port}/jnlpJars/slave.jar")" =~ ^HTTP/[0-9.]+\ 2 ]]