More exception handlers in ipa-client-install
Added exception handler to certutil operation of adding CA to the
default NSS database. If operation fails, installation is aborted and
changes are rolled back.
https://fedorahosted.org/freeipa/ticket/2415
If obtaining host TGT fails, the installation is aborted and changes are
rolled back.
https://fedorahosted.org/freeipa/ticket/1995