quote variables in shell conditionals

Fix incorrect evaluation of -n tests for CRC_BUNDLE, HTTP_PROXY,
and HTTPS_PROXY variables. Without quotes, the test evaluates to
true even when variables are unset or empty, causing spurious
error messages:

  ERRO Please provide a configuration property and its value
  as in 'crc config set KEY VALUE'

Quote the variables in conditional expressions so that -n
correctly evaluates to false for empty or unset values.

Author: lpiwowar

devsetup/scripts/crc-setup.sh

@@ -53,13 +53,13 @@ ${CRC_BIN} config set skip-check-daemon-systemd-sockets true
 ${CRC_BIN} config set cpus ${CPUS}
 ${CRC_BIN} config set memory ${MEMORY}
 ${CRC_BIN} config set disk-size ${DISK}
-if [ -n ${HTTP_PROXY} ]; then
+if [ -n "${HTTP_PROXY}" ]; then
     ${CRC_BIN} config set http-proxy ${HTTP_PROXY}
 fi
-if [ -n ${HTTPS_PROXY} ]; then
+if [ -n "${HTTPS_PROXY}" ]; then
     ${CRC_BIN} config set https-proxy ${HTTPS_PROXY}
 fi
-if [ -n ${CRC_BUNDLE} ]; then
+if [ -n "${CRC_BUNDLE}" ]; then
     ${CRC_BIN} config set bundle ${CRC_BUNDLE}
 fi
 if [ "$CRC_MONITORING_ENABLED" = "true" ]; then