JIRA does not stop and start correctly when the servlet context is pulled down. Makes supportting JIRA harder

When JIRA 4.0 is stopped and started, the servlet context is torn down and re-run however JIRA has JVM global variables that are still in effect and hence its not really a clean start.

For example lets say a customer gets in the state where the lock file is still in the JIRA home directory. They will stop JIRA, remove the file and restart JIRA.,

However the global variable that marks that the home directory lock file in in place it still set and hence JIRA wont start.

We need to tear down any global variables on servlet context init and re-evaluate them each time.

Without this fix, we are going to incur extra support costs.