shell: Escape literal end bracket in "case" patterns.

shell/caucase.sh

@@ -778,7 +778,7 @@ EOF
               ca_port=80
               # Note: too bad there is no portable case fall-through...
               case "$ca_netloc" in
-                *]:*)
+                *\]:*)
                   # Bracket-enclosed address, which may contain colons
                   ca_address="$(
                     printf "%s\\n" "$ca_netloc" | sed "s!^\\(.*\\]\\).*!\\1!"
@@ -787,7 +787,7 @@ EOF
                     printf "%s\\n" "$ca_netloc" | sed "s!^[^\\]]*\\]:!!"
                   )"
                 ;;
-                *]*)
+                *\]*)
                   # Bracket-enclosed address, which may contain colons
                   ca_address="$(
                     printf "%s\\n" "$ca_netloc" | sed "s!^\\(.*\\]\\).*!\\1!"