Fix generate CSR submit

Add .prevent modifier to prevent native form submit in
CSR modal which causes unwanted page refresh.

Signed-off-by: Yoshie Muranaka <yoshiemuranaka@gmail.com>
Change-Id: I3d56ed4797bc3829507873029d849a7a1ad03c99
diff --git a/src/views/AccessControl/SslCertificates/ModalGenerateCsr.vue b/src/views/AccessControl/SslCertificates/ModalGenerateCsr.vue
index 3f53c41..bb74c19 100644
--- a/src/views/AccessControl/SslCertificates/ModalGenerateCsr.vue
+++ b/src/views/AccessControl/SslCertificates/ModalGenerateCsr.vue
@@ -12,7 +12,7 @@
       @cancel="resetForm"
       @hidden="$v.$reset()"
     >
-      <b-form id="generate-csr-form" novalidate @submit="handleSubmit">
+      <b-form id="generate-csr-form" novalidate @submit.prevent="handleSubmit">
         <b-container fluid>
           <b-row>
             <b-col lg="9">