Fix multi-meter_inject error msg

Was trying to coerce the exception class
to string rather than calling .message
Results in a stacktrace.

FIXRM #8460
Mark broken tests as pending

These tests are broken a few different ways.

[SeeRM #8463]

also see: https://github.com/rapid7/metasploit-framework/pull/2477
Land #2486 - Fix error message backtrace
Land #2487 - Mark broken tests as pending