Create prosody modules directory if needed

src/freedombone-app-xmpp

                 tar -xzvf $prosody_modules_filename
                 if [ -d prosody-modules ]; then
                     systemctl stop prosody
+                    if [ ! -d /var/lib/prosody/prosody-modules ]; then
+                        mkdir /var/lib/prosody/prosody-modules
+                    fi
                     cp -r prosody-modules/* /var/lib/prosody/prosody-modules
                     chown -R prosody:prosody /var/lib/prosody/prosody-modules
                     systemctl start prosody
 
     # install modules
     update_prosody_modules initial
+    if [ ! -d /var/lib/prosody/prosody-modules ]; then
+        echo $'No prosody modules available'
+    fi
 
     # create a certificate
     if [[ "$(cert_exists ${DEFAULT_DOMAIN_NAME} pem)" == "0" ]]; then