Fix haproxy 1.6 compile error

[gdbtek]

gcc  -g -o haproxy-systemd-wrapper src/haproxy-systemd-wrapper.o   
install -d "/opt/haproxy/sbin"
install haproxy "/opt/haproxy/sbin"
install haproxy-systemd-wrapper "/opt/haproxy/sbin"
install -d "/opt/haproxy/share/man"/man1
install -m 644 doc/haproxy.1 "/opt/haproxy/share/man"/man1
install -d "/opt/haproxy/doc/haproxy"
for x in configuration architecture haproxy-en haproxy-fr; do \
        install -m 644 doc/$x.txt "/opt/haproxy/doc/haproxy" ; \
    done
install: cannot stat ‘doc/haproxy-en.txt’: No such file or directory
install: cannot stat ‘doc/haproxy-fr.txt’: No such file or directory
make: *** [install-doc] Error 1

[gdbtek]

fixed