Increase the default buffer capacity to 100K (#752)

We've received reports that the default in-flight limit may be too
small. Now that the proxy can consume multiple cores, it seems wise to
increase the default from 10K to 100K.

This bound should prevent high-traffic workloads from hitting the
in-flight limit in all but extreme cases, while still protecting the
proxy against infinite growth.

Author: olix0r

linkerd/app/src/env.rs

@@ -189,8 +189,8 @@ const DEFAULT_RESOLV_CONF: &str = "/etc/resolv.conf";
 const DEFAULT_INITIAL_STREAM_WINDOW_SIZE: u32 = 65_535; // Protocol default
 const DEFAULT_INITIAL_CONNECTION_WINDOW_SIZE: u32 = 1048576; // 1MB ~ 16 streams at capacity
 
-// 10_000 is arbitrarily chosen for now...
-const DEFAULT_BUFFER_CAPACITY: usize = 10_000;
+// 100_000 is arbitrarily chosen for now...
+const DEFAULT_BUFFER_CAPACITY: usize = 100_000;
 
 // This configuration limits the amount of time Linkerd retains cached clients &
 // connections.