BUG/MINOR: cfgparse-quic: fix bbr initialization

BUG/MINOR: cfgparse-quic: fix bbr initialization

To support pacing with cubic, a recent change was introduced to render
quic_cc_algo on bind line dynamically allocated, instead of pointing to
a globally defined variable. This allows customization of the algorithm
callbacks per bind line.

This was not correctly used for BBR as it was set to point to the global
quic_cc_algo_bbr. This causes a segfault on haproxy process closing. Fix
this by properly initializing BBR as other algorithms.

This should fix coverity report from github issue #2786.