Keep trimming when pct fstrim fails on one container

pct fstrim exits 255 when the container is locked, for example while a
backup runs ("CT is locked (backup)"). Under errexit the command
substitution ended the whole run there, before the output check below it
and before the remaining containers, and telemetry filed it as
"DPKG: Fatal internal error". Print the result and go on instead.

CHANGELOG.md

@@ -581,14 +581,7 @@ Exercise vigilance regarding copycat or coat-tailing sites that seek to exploit
 
 ### 💾 Core
 
-  - fix: put the reason for a VM failure into its trace [@MickLesk](https://github.com/MickLesk) ([core#200](https://github.com/community-scripts/core/pull/200))
-- fix: check the bridge before creating a container, and its state after start [@MickLesk](https://github.com/MickLesk) ([core#199](https://github.com/community-scripts/core/pull/199))
-- ref: offer to remove only the container this run created [@MickLesk](https://github.com/MickLesk) ([core#198](https://github.com/community-scripts/core/pull/198))
-- feat: report a cancelled tool dialog as an abort and name the failing command [@MickLesk](https://github.com/MickLesk) ([core#197](https://github.com/community-scripts/core/pull/197))
-- feat: check KVM and the host's threads before building a VM [@MickLesk](https://github.com/MickLesk) ([core#196](https://github.com/community-scripts/core/pull/196))
-- ref: give a host tool one log file for the whole run [@MickLesk](https://github.com/MickLesk) ([core#194](https://github.com/community-scripts/core/pull/194))
-- fix: keep a piped stdin when output moves to the log after a hangup [@MickLesk](https://github.com/MickLesk) ([core#193](https://github.com/community-scripts/core/pull/193))
-- fix: pve-LXC: say when the container went away during its setup [@MickLesk](https://github.com/MickLesk) ([core#192](https://github.com/community-scripts/core/pull/192))
+  - fix: pve-LXC: say when the container went away during its setup [@MickLesk](https://github.com/MickLesk) ([core#192](https://github.com/community-scripts/core/pull/192))
 - fix: treat Esc in a VM wizard dialog as leaving the script [@MickLesk](https://github.com/MickLesk) ([core#190](https://github.com/community-scripts/core/pull/190))
 - ref: count a container stopped during a detached install as an abort [@MickLesk](https://github.com/MickLesk) ([core#187](https://github.com/community-scripts/core/pull/187))
 - feat: find the assets of a renamed GitHub repo without the API [@MickLesk](https://github.com/MickLesk) ([core#188](https://github.com/community-scripts/core/pull/188))

tools/pve/fstrim.sh

@@ -118,7 +118,8 @@ function trim_container() {
   fi
 
   local fstrim_output
-  fstrim_output=$(pct fstrim "$container" 2>&1)
+  # pct fstrim fails on a locked CT (e.g. a running backup); report it and go on.
+  fstrim_output=$(pct fstrim "$container" 2>&1) || true
   if echo "$fstrim_output" | grep -qi "not supported"; then
     echo -e "${RD}fstrim isnt supported on this storage!${CL}"
   elif echo "$fstrim_output" | grep -Eq '([0-9]+(\.[0-9]+)?\s*[KMGT]?B)'; then