Error message of wrong config should be more comprehensible

[LiXi-storage]

Following error messages are printed if /etc/esmon_install.conf is invalid. But it is not helpful to understand where the problem is.

[ERROR] [esmon_config.py:2043] config option [host_id] is not configured and has no default value
[ERROR] [esmon_install_nodeps.py:2428] failed to parse config [/etc/esmon_install.conf]