scaletempo: Advertise interleaved layout in caps templates

Scaletempo doesn't support non-interleaved layout. Not explicitely stating this
would trigger critical warnings and a caps negotiation failure when scaletempo
is used as playbin audio-filter.

Patch suggested by George Kiagiadakis <george.kiagiadakis@collabora.com>.

Fixes #591
14 jobs for <span class="ref-name">scaletempo-interleaved</span> in 97 minutes and 58 seconds (queued for 26 seconds)
Status Job ID Name Coverage
  Preparation
passed #257061
gst indent

00:00:29

passed #257060
manifest

00:00:51

 
  Build
passed #257062
build fedora x86_64

00:06:04

passed #257063
build nodebug fedora x86_64

00:11:16

 
  Test
passed #257064
check fedora

00:03:22

passed #257065
integration testsuites fedora

00:10:16

 
  Full Builds
passed #257067
build cerbero android universal

00:12:34

passed #257068
build cerbero cross win32

00:10:48

passed #257069
build cerbero cross win64

00:06:36

passed #257066
build cerbero fedora x86_64

00:07:26

 
  Full Tests
passed #257071
valgrind bad

00:17:47

passed #257072
valgrind ges

00:05:57

passed #257070
valgrind good

00:09:13

 
  Apps
passed #257073
android universal examples

00:10:10