baseparse: Don't do buffer dropping in passthrough mode

Passthrough is supposed to pass buffers through, so don't clip them
then, especially as the subclass might not even have called
gst_base_parse_set_frame_rate in passthrough mode to set up the
lead_in_ts and lead_out_ts private member variables. This is common,
as it's usually done in their handle_frame implementation, which
doesn't even get called in passthrough push mode.
As an extra safety, also don't do the buffer dropping if
gst_base_parse_set_frame_rate hasn't been called with proper data,
which can be checked based on whether there's a valid frame_duration.
24 jobs for baseparse-no-passthrough-clip in 107 minutes and 39 seconds (queued for 4 minutes and 30 seconds)
latest
Status Job ID Name Coverage
  Preparation
passed #420768
gst indent

00:00:28

passed #420767
manifest

00:00:38

 
  Build
passed #420774
build cerbero android universal

00:17:06

passed #420775
build cerbero cross win32

00:09:57

passed #420776
build cerbero cross win64

00:11:42

passed #420773
build cerbero fedora x86_64

00:09:02

manual #420778
gst-ios-12.2 allowed to fail manual
build cerbero ios universal
passed #420777
gst-macos-10.14
build cerbero macos x86_64

00:06:50

passed #420769
build fedora x86_64

00:08:04

passed #420770
build nodebug fedora x86_64

00:04:46

passed #420771
build static fedora x86_64

00:14:17

passed #420772
build static nodebug fedora x86_64

00:11:35

 
  Test
failed #421390
check fedora

00:03:59

passed #420780
integration testsuites fedora

00:10:35

passed #420785
valgrind bad

00:07:25

passed #420782
valgrind base

00:12:21

failed #420781
valgrind core

00:25:22

passed #420786
valgrind ges

00:05:53

passed #420783
valgrind good

00:11:28

passed #420784
valgrind ugly

00:02:25

failed #420959
check fedora

00:03:45

failed #420779
check fedora

00:06:03

 
  Integrate
skipped #420787
android universal examples
skipped #420788
documentation
 
Name Stage Failure
failed
check fedora Test
           Total: 3105
Uploading artifacts...
gst-build/build/meson-logs/: found 2 matching files
validate-logs: found 3523 matching files

Uploading artifacts to coordinator... ok
id=421390 responseStatus=201 Created token=9G1yf6C2
Uploading artifacts...
validate-logs/*.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=421390 responseStatus=201 Created token=9G1yf6C2
ERROR: Job failed: exit code 1
failed
valgrind core Test
           Total: 851
Uploading artifacts...
gst-build/build/meson-logs/: found 2 matching files
validate-logs: found 1811 matching files

Uploading artifacts to coordinator... ok
id=420781 responseStatus=201 Created token=CizLBAmn
Uploading artifacts...
validate-logs/*.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=420781 responseStatus=201 Created token=CizLBAmn
ERROR: Job failed: exit code 1