server: terminal width should fallback to 80x25. (#1895)

Some environments might disable access to `/dev/tty`, fall
back to '80' in such scenarios.

Move to 'cheggaaa/pb' package for better cross platform
support on fetching terminal width.

Fixes #1891

vendor/github.com/cheggaaa/pb/pool_x.go

@@ -0,0 +1,22 @@
+// +build linux darwin freebsd netbsd openbsd solaris dragonfly
+
+package pb
+
+import "fmt"
+
+func (p *Pool) print(first bool) bool {
+	var out string
+	if !first {
+		out = fmt.Sprintf("\033[%dA", len(p.bars))
+	}
+	isFinished := true
+	for _, bar := range p.bars {
+		if !bar.isFinish {
+			isFinished = false
+		}
+		bar.Update()
+		out += fmt.Sprintf("\r%s\n", bar.String())
+	}
+	fmt.Print(out)
+	return isFinished
+}