[services] Clean up run_server_image.sh

Summary: Cleaned up run_server_image.sh with style fixes and some double quoting to safely prevent globbing and word splitting. More details in inline comments.

Test Plan: ShellCheck, close reading.

Reviewers: ashoat, karol-bisztyga, atul

Reviewed By: ashoat

Subscribers: palys-swm, Adrian

Differential Revision: https://phab.comm.dev/D4398