.navbar-brand > img [Fixed issue #15222]

I changed a line to resolve issue 15222
/less/navbar.less @line 177
    display: block;
to
    display: line-block;

https://github.com/twbs/bootstrap/issues/15222
it seems to be included to v3.3.2....

+first commit. if this commit does not need to resolve that issue, let me know.