Make git-p4 support handle P4PORT environment variable.
Review Request #5243 — Created Jan. 13, 2014 and submitted
Make git-p4 support handle P4PORT environment variable.
The git-p4 support in rbtools only worked if you had git-p4.port in the git
config. If users had P4PORT in their environment instead of using this config
key, it wouldn't detect the repo as being a git-p4 clone.
Used rbt post with my git-p4 clone.
