tools/create-openbsd: bump up the limits for syz-bit

As syz-bot became much more aggressive about resource usage lately it
started running over the limits and is getting blocked. Give it all
the rope it wants. There's nothing else on the VM anyway.

Used the vmd class as it is given the most memory in login.conf.
diff --git a/tools/create-openbsd-gce-ci.sh b/tools/create-openbsd-gce-ci.sh
index bdba48b..66f1846 100755
--- a/tools/create-openbsd-gce-ci.sh
+++ b/tools/create-openbsd-gce-ci.sh
@@ -66,11 +66,11 @@
   echo "starting syz-ci"
   fsck -y /dev/sd1a
   mount /syzkaller
-  su -l syzkaller <<EOF2
+  su -c vmd -l syzkaller <<EOF2
     cd /syzkaller
     export HOME=/syzkaller
     set -eux
-    ulimit -d 8000000
+    ulimit -n 1024 -d 16000000
     mkdir -p /syzkaller/go-cache
     export GOCACHE=/syzkaller/go-cache
     test -d /syzkaller/gopath/src/github.com/google/syzkaller || (