jaeger-agent --reporter.grpc.tls.enabled=true fails on windows

[wscheele]

Describe the bug
Due to golang/go#16736, the jaeger-agent is unable to setup a connection to a tls grpc reporter endpoint on windows.

Error message:

{"level":"fatal","ts":1602401908.4807255,"caller":"command-line-arguments/main.go:67","msg":"Could not create collector proxy","error":"failed to load TLS config: failed to load CA CertPool: failed to load SystemCertPool: crypto/x509: system root pool is not available on Windows","stacktrace":"main.main.func1\n\tcommand-line-arguments/main.go:67\ngithub.com/spf13/cobra.(*Command).execute\n\tgithub.com/spf13/cobra@v0.0.3/command.go:762\ngithub.com/spf13/cobra.(*Command).ExecuteC\n\tgithub.com/spf13/cobra@v0.0.3/command.go:852\ngithub.com/spf13/cobra.(*Command).Execute\n\tgithub.com/spf13/cobra@v0.0.3/command.go:800\nmain.main\n\tcommand-line-arguments/main.go:102\nruntime.main\n\truntime/proc.go:204"}

To Reproduce
Steps to reproduce the behavior:

1. run jaeger-agent.exe with --reporter.grpc.tls.enabled=true

Expected behavior
It works

Version (please complete the following information):

• OS: Windows
• Jaeger version: v1.20.0

Additional context
golang/go#16736
sensu/sensu-go#4018