vstest is failing in recent runs due to "generate coverage" step failing

[anilkpan]

vstest is failing in recent runs for several PRs due to "Generate coverage" step failing. Here is the error log:

---

##[debug] /agent/_work/_temp/b5d76725-58f5-4bb8-838f-a57eb555625e.sh
/usr/bin/bash --noprofile --norc /agent/_work/_temp/b5d76725-58f5-4bb8-838f-a57eb555625e.sh

• reportgenerator -reporttypes:Cobertura '-reports:tests/*coverage.xml' -targetdir:.
  /agent/_work/_temp/b5d76725-58f5-4bb8-838f-a57eb555625e.sh: line 2: reportgenerator: command not found

##[debug]Exit code 127 received from tool '/usr/bin/bash'
##[debug]STDIO streams have closed for tool '/usr/bin/bash'
##[error]Bash exited with code '127'.
##[debug]Processed: ##vso[task.issue type=error;source=TaskInternal;]Bash exited with code '127'.
##[debug]task result: Failed
##[debug]Processed: ##vso[task.complete result=Failed;done=true;]
Finishing: Generate coverage.xml

For example, the following PRs have this failure:
#3313
#3143
#3329