GHA: try workaround for slow Azure Ubuntu distro server (cont.)

- fail if all retries failed.
- run `dpkg --configure -a` after an aborted slow attempt.

```
Selecting previously unselected package libsys-hostname-long-perl.
Error: slow server, retry
E: dpkg was interrupted, you must manually run 'sudo dpkg --configure -a' to correct the problem.
[...]
```

Bug: https://github.com/curl/curl/pull/21107#issuecomment-4163506100
Follow-up to 5172ba5475 #21107

Closes #21181

.github/workflows/distcheck.yml

@@ -288,7 +288,9 @@ jobs:
             sha256sum pkg.bin && sha256sum pkg.bin | grep -qwF -- "${OLD_CMAKE_SHA256_WIN_INTEL}" && unzip -q pkg.bin && rm -f pkg.bin
             printf '%s' ~/cmake-"${OLD_CMAKE_VERSION}"-win64-x64/bin/cmake.exe > ~/old-cmake-path.txt
           elif [[ "${MATRIX_IMAGE}" = *'ubuntu'* ]]; then
-            printf '#!/bin/sh\nfor i in 1 2 3; do timeout 30 "$@" && break; echo "Error: slow server, retry"; sleep 1; done' > "$HOME"/my-apt; chmod +x "$HOME"/my-apt
+            printf "#!/bin/sh
+              while [ \$? = 0 ]; do for i in 1 2 3; do timeout 30 \"\$@\" && break 2; echo \"Error: slow server, retry \$i\"; sleep 1
+              dpkg --configure -a; done; false; done" > "$HOME"/my-apt; chmod +x "$HOME"/my-apt
             sudo "$HOME"/my-apt apt-get -o Dpkg::Use-Pty=0 install libpsl-dev libssl-dev
             cd ~
             curl --disable --fail --silent --show-error --connect-timeout 15 --max-time 60 --retry 3 --retry-connrefused \