VistAPackageInfoFetcher: improve robustness of isPatchInstalled method
VistAPackageInfoFetcher: improve robustness of isPatchInstalled method

Also add some extra comments.

OSEHRA-Id: http://issues.osehra.org/browse/VAF-122
Change-Id: Ie7bcf7678b68e495aeffa2455d409a9407807893

apexdatasolutions/VistA,josephsnyder/VistA,OSEHRA/VistA,OSEHRA/VistA,shabiel/VistA,shabiel/VistA,OSEHRA-Sandbox/VistA,mdgeek/VistA-FHIR-CWF,OSEHRA-Sandbox/VistA,timmvt/VistA_tt,jasonli2000/VistA,shabiel/VistA,OSEHRA-Sandbox/VistA,josephsnyder/VistA,josephsnyder/VistA,apexdatasolutions/VistA,apexdatasolutions/VistA,mdgeek/VistA-FHIR-CWF,shabiel/VistA,apexdatasolutions/VistA,timmvt/VistA_tt,timmvt/VistA_tt,OSEHRA/VistA,josephsnyder/VistA,josephsnyder/VistA,jasonli2000/VistA,shabiel/VistA,OSEHRA/VistA,shabiel/VistA,josephsnyder/VistA,mdgeek/VistA-FHIR-CWF,jasonli2000/VistA,timmvt/VistA_tt,jasonli2000/VistA,OSEHRA-Sandbox/VistA,OSEHRA/VistA,apexdatasolutions/VistA,mdgeek/VistA-FHIR-CWF,timmvt/VistA_tt,OSEHRA-Sandbox/VistA,mdgeek/VistA-FHIR-CWF,OSEHRA/VistA,mdgeek/VistA-FHIR-CWF,OSEHRA-Sandbox/VistA