alsa pcm plugin: fix capture delay reporting #606

Job	Run time
check (--enable-debug)	42s
check (--enable-debug)	42s
sanitize-prepare	8s
sanitize-prepare	8s
check (--enable-debug --enable-aac --enable-msbc --enable-lc3-swb)	41s
check (--enable-debug --enable-aac --enable-msbc --enable-lc3-swb)	41s
check (--enable-debug --enable-mp3lame --enable-mpg123)	53s
check (--enable-debug --enable-mp3lame --enable-mpg123)	53s
check (--enable-faststream --enable-midi --enable-mp3lame)	43s
check (--enable-faststream --enable-midi --enable-mp3lame)	43s
check (--enable-ofono --enable-opus --enable-upower)	46s
check (--enable-ofono --enable-opus --enable-upower)	38s
check (--disable-aplay --enable-rfcomm --enable-manpages)	50s
check (--disable-aplay --enable-rfcomm --enable-manpages)	50s
check (--disable-ctl --enable-aptx --enable-aptx-hd --with-libopenaptx)	47s
check (--disable-ctl --enable-aptx --enable-aptx-hd --with-libopenaptx)	47s
sanitize (address alignment bool bounds nonnull-attribute shift undefined)	1m 18s
sanitize (address alignment bool bounds nonnull-attribute shift undefined)	1m 18s
sanitize (thread)	2m 10s
sanitize (thread)	2m 10s
	17m 48s

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