splitmuxsink: Only set running time on finalizing sink element when in async-finalize mode

There is only a single sink element in async-finalize mode, and we would
keep the running time from previous fragments set in that case. As we
don't ever set the running time for the very last fragment on EOS, this
would mean that the closing time reported for the very last fragment is
the same as the closing time of the previous fragment.
16 jobs for splitmuxsink-async-eos in 50 minutes and 36 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Preparation
passed #322187
gst indent

00:00:17

passed #322186
manifest

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  Build
passed #322188
build fedora x86_64

00:05:05

passed #322189
build nodebug fedora x86_64

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  Test
passed #322190
check fedora

00:03:53

passed #322191
integration testsuites fedora

00:09:33

 
  Full Builds
passed #322193
build cerbero android universal

00:10:29

passed #322194
build cerbero cross win32

00:07:08

passed #322195
build cerbero cross win64

00:06:49

passed #322192
build cerbero fedora x86_64

00:06:13

 
  Full Tests
passed #322197
valgrind bad

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passed #322198
valgrind ges

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passed #322316
valgrind good

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failed #322196
valgrind good

00:08:07

 
  Apps
passed #322199
android universal examples

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  Deploy
passed #322200
documentation

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