Coredump in redis proxy using hostname in config file

## Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
If possible, provide a recipe for reproducing the error.
To start a redis proxy in tjwqtst-staging cluster, set hostname to host.x in config file. When bootstrap it, the application coredump.
2. What did you expect to see?
runs well
3. What did you see instead?
coredump
4. What version of Pegasus are you using?
v1.12.2

No file or test is named. Begin by reproducing the v1.12.2 redis proxy bootstrap with hostname host.x in the configuration, then trace the failure from bootstrap into hostname handling. Done means the proxy starts without a coredump and runs normally with that configuration.

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