BUILD: cirrus-ci: workaround "pkg install" bug

there's a bug https://github.com/freebsd/pkg/issues/902
adding "pkg update -f && pkg upgrade -y" is workaround.
diff --git a/.cirrus.yml b/.cirrus.yml
index d528083..5c7c840 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -6,7 +6,7 @@
       image_family: freebsd-11-3-snap
   only_if: $CIRRUS_BRANCH =~ 'master|next'
   install_script:
-    - pkg install -y openssl git gmake lua53 socat
+    - pkg update -f && pkg upgrade -y && pkg install -y openssl git gmake lua53 socat
   script:
     - git clone https://github.com/VTest/VTest.git ../vtest
     - make -C ../vtest