Update quay.io/kubespray/vagrant (#8605)

quay.io/kubespray/vagrant image is used for molecule_tests.
The tag was v2.17.1 on release-2.18 branch but the image
contains vagrant-2.2.15 which has a bug related to a virtual machine creation.
That caused kubespray CI failures.
This updates the image to use a newer vagrant.

.gitlab-ci/vagrant.yml

@@ -4,7 +4,7 @@ molecule_tests:
   tags: [c3.small.x86]
   only: [/^pr-.*$/]
   except: ['triggers']
-  image: quay.io/kubespray/vagrant:$KUBESPRAY_VERSION
+  image: quay.io/kubespray/vagrant:v2.18.0
   services: []
   stage: deploy-part1
   before_script:
@@ -33,7 +33,7 @@ molecule_tests:
   tags: [c3.small.x86]
   only: [/^pr-.*$/]
   except: ['triggers']
-  image: quay.io/kubespray/vagrant:$KUBESPRAY_VERSION
+  image: quay.io/kubespray/vagrant:v2.18.0
   services: []
   before_script:
     - apt-get update && apt-get install -y python3-pip