fix i3bar crashing when I3SOCK present (#2471)
fix i3bar crashing when I3SOCK present (#2471)

When I3SOCK is present, socket_path might be a pointer to an
environment variable, which cannot be free'd in line 157. This
commit duplicates the string if I3SOCK is present, thus making
socket_path a free-able pointer again.
cornerman/i3,Airblader/i3-original,cornerman/i3,stapelberg/i3,strake/i3,acrisci/i3,i3/i3,avrelaun/i3,Airblader/i3-original,shdown/i3,acrisci/i3,Airblader/i3-original,Airblader/i3-original,avrelaun/i3,Airblader/i3,strake/i3,strake/i3,acrisci/i3,Airblader/i3,avrelaun/i3,cornerman/i3,cornerman/i3,Airblader/i3,acrisci/i3,acrisci/i3,stapelberg/i3,i3/i3,shdown/i3,i3/i3,i3/i3,strake/i3,Airblader/i3-original,Airblader/i3,avrelaun/i3,stapelberg/i3,shdown/i3,shdown/i3,strake/i3,stapelberg/i3