Allow git.current_branch to work with git<1.7.8

"git branch" and "git branch --list" are functionally identical, but the
"--list" parameter was not added to git until version 1.7.8, so older
versions of git (such as the one in the RHEL/CentOS 6 repositories) are
unable to successfully run this function.

This commit removes the "--list" from the git command used in this
function.
Merge pull request #9472 from gravyboat/develop

Cloud Troubleshooting doc version compatibility notes.
Merge pull request #9470 from terminalmage/issue9468

Allow git.current_branch to work with git<1.7.8
Fix sphinx build warning

This fixes a sphinx build warning resulting from improperly formatted
argument names.
Enhancement to master troubleshooting docs

Made some of the language more concise, and improved the example on
setting resource limits. /etc/security/limits.d/NN-something.conf is
the generally preferred method of setting resource limits.
Merge pull request #9478 from terminalmage/sphinx

Fix sphinx build warning
Merge pull request #9479 from terminalmage/docs

Enhancement to master troubleshooting docs
Fixed a lower case reference to Salt on the cloud troubleshooting docs.