The continuous deployment script `update-grid-servers` has numerous basic shell errors and incorrect assumptions which cause it to fail

• GitLab will invoke it with "staging" as a gridname but morph knows the grid as "testing"
• The names of nodes in a grid are unqualified and cannot be resolved in the CI environment
• The names of the nodes extracted from the Nix configuration are presented as a json list and then iterated over in the shell as if it were a string containing whitespace-separated names
• The loop for iterating over nodes is terminated with incorrect syntax