use more descriptive func name for mapper

try

@@ -294,7 +294,7 @@ EOF
     export SOCKET
 
     # Running mapper in a subshell to suppress job control [1] + Done message
-    (mapper&)
+    (uid_gid_mapper&)
 
     # --mount: mounting and unmounting filesystems will not affect the rest of the system outside the unshare
     # --user: the process will have a distinct set of UIDs, GIDs and capabilities.
@@ -559,7 +559,7 @@ error() {
 # Change uid/gid mapping
 ################################################################################
 
-mapper() {
+uid_gid_mapper() {
     cat "$SOCKET" > /dev/null
     # Get the pid of the unshare process with current pid as parent
     pid=$(pgrep -P $$ -f unshare)