Clean up test-family-matching test.

Correct the type of TestMatchPattern's 'ret' from TestResult to
TestMatchResult to match the actual return type (and values assigned to
it).

Fix leak of TestMatchPattern's 'xml' and TestFamily's 'pat'.

Simplify TestMatchPattern cleanup and ensure cleanup always happens.
10 jobs for cleanup_family_matching_test in 6 minutes and 37 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Build
passed #6507269
gst-macos-10.15
meson macos

00:02:24

passed #6507266
meson-mingw-w64-build

00:05:22

manual #6507270
docker windows 1809 allowed to fail manual
meson msys2
passed #6507264
meson-shared-build

00:05:24

passed #6507265
meson-static-build

00:03:20

passed #6507267
docker windows 1809
meson vs2017 amd64

00:01:22

passed #6507268
docker windows 1809
meson vs2017 x86

00:01:21

passed #6507263
mingw-build

00:06:36

passed #6507261
shared-build

00:04:52

passed #6507262
static-build

00:03:48