SOSCommandResult - getExitCode handling

Note: Internal task - for documentation purposes

Current Situation

• With JITL-696, the SOSCommandResult.getExitCode() getter method was changed to return 0 if exitCode = null.
• However, null is a valid value - for example, when a command execution ends with an exception and no exit code is provided.
• This change affects other components that explicitly check for exitCode = null; due to this change, that check will never be true.

Desired Behaviour

• The getExitCode() method should return the actually set value and not substitute it with a fake value.
• Multiple sources should be updated to handle this behavior correctly.

Maintainer notes

• Affected dependent classes:
  • com.sos.jitl.jobs.db.oracle.SQLPLUSJob
  • com.sos.jitl.jobs.ssh.SSHJob
  • com.sos.commons.git.GitCommand
  • com.sos.commons.vfs.ssh.commons.SSHServerInfo