jbuf: set start value for jb->faults

This avoids that jb->min is reduced immediately after start in adaptive mode.
The user may set jb->min to some positive value if he expects that re-ordered
packets will occur. After the start of an incoming RTP stream the occurrence of
re-ordered packets should be observed before jb->min is reduced.

src/jbuf/jbuf.c

@@ -184,6 +184,7 @@ int jbuf_alloc(struct jbuf **jbp, uint32_t min, uint32_t max)
 	jb->jbtype = JBUF_FIXED;
 	jb->min  = min;
 	jb->max  = max;
+	jb->faults = JBUF_FAULT_HI / 2;
 
 	DEBUG_INFO("alloc: delay=%u-%u frames\n", min, max);