BUG 1211 - deletion non existing target returns 500

It is checked whether data at specified path exists (via method
readConfigurationData). If it isn't so then HTTP response returning code
is set to 200.

Change-Id: I0c0f51c144ffc430ac5bcef118f485f84ae25207
Signed-off-by: Jozef Gloncak <jgloncak@cisco.com>
Merge "BUG 1211 - deletion non existing target returns 500"