lib: crash when FRR hostname length > 80 chars

lib: crash when FRR hostname length > 80 chars

Although the RFC states hostname length should be < 255 chars,
FRR allows infinite length technically. However, when you try
to set a hostname > 80 chars, you would immediately notice a crash.

RCA: Crash due to buffer overflow. Large buffer sprintf'd into smaller
buffer. Usage of sprintf function instead of snprintf which is safer.

Signed-off-by: Lakshman Krishnamoorthy <lkrishnamoor@vmware.com>