bgpd: increase buffer size to store ecomunity as a string

bgpd: increase buffer size to store ecomunity as a string

On the case where an ecom from FS redirect is received, the ecom may be
with the format A.B.C.D:E. On this case, the printable format of the
Flowspec redirect VRF ecom value may use more bytes in the buffer
dedicated for that. The buffer that stores the ecommunity is increased.

Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>