software/slaprunner: Change directory in a subshell.

More similar changes will come later as part of larger changes.
Also, fail if
  cd "$backup_directory"
fails, as it is supposed to exist by that point.

software/slaprunner/buildout.hash.cfg

@@ -31,7 +31,7 @@ md5sum = 9db9957f452bda370cb2d5cc2e833e85
 
 [template-runner-export-script]
 filename = template/runner-export.sh.jinja2
-md5sum = c4e78e85235fd7340029b26c54f4992f
+md5sum = 5cc9829a25d129740158e97c9899bbfa
 
 [instance-runner-export]
 filename = instance-runner-export.cfg.in

software/slaprunner/template/runner-export.sh.jinja2

@@ -63,7 +63,10 @@ if [ -d {{ directory['backup'] }}/runner/software ]; then
   rm {{ directory['backup'] }}/runner/software/*
 fi
 
-cd {{ directory['backup'] }} && find -type f ! -name backup.signature -print0 | xargs -0 sha256sum | LC_ALL=C sort -k 66 > backup.signature
+(
+  cd "$backup_directory"
+  find -type f ! -name backup.signature -print0 | xargs -0 sha256sum | LC_ALL=C sort -k 66 > backup.signature
+)
 
 # Check that export didn't happen during backup of instances
 tmp_backup_sum=$(mktemp -p "$tmp_directory")