HisAppraiser: Skipped measurements validation if not needed

This patch fixes a bug in the constructor of class HisReportValidator.
The class is used in two way, validating current report and just
parsing the received report string.
In the second case, the constructor receives only the report string
and the validation of the measurements must be skipped. Otherwise,
since the machineName is missing it's not possible to obtain the
pcrIMLMask and an exception is raised.

Signed-off-by: Nicola Barresi <nicola.barresi@polito.it>
Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
HisAppraisr: Fixed error message in case of wrong PCRs passed to analysis

This patch fixes a bug in validation of PCRs passed to the analysis.
If the given PCR is out of the range [0-23] an exception was thrown,
but it was catched and a wrong error message was displayed.

Signed-off-by: Nicola Barresi <nicola.barresi@polito.it>
Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Merge branch '1.6-pcrIMLMask-bugfixes' for bug fixing