refactor: make mystamps.conf source-able by quoting a value with spaces

Part of #383

[skip ci]

Author: php-coder

infra/vagrant/provisioning/roles/mystamps-app/templates/mystamps.conf

@@ -1,3 +1,3 @@
 # This file is being read and used by /etc/systemd/system/mystamps.service
 SPRING_PROFILES_ACTIVE={{ profile }}
-JAVA_OPTS=-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/data/heap-dumps -XX:+UseCompressedOops -Dsun.rmi.dgc.client.gcInterval=86400000 -Dsun.rmi.dgc.server.gcInterval=86400000 -Djava.security.egd=file:/dev/./urandom -Xmx128m -Xss256k
+JAVA_OPTS='-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/data/heap-dumps -XX:+UseCompressedOops -Dsun.rmi.dgc.client.gcInterval=86400000 -Dsun.rmi.dgc.server.gcInterval=86400000 -Djava.security.egd=file:/dev/./urandom -Xmx128m -Xss256k'