change git pull" to use "git fetch && git reset --hard origin/master"

```
Debug: Exec[rbenv::plugin::update teamcity-agent ruby-build](provider=posix): Executing 'git pull'
Debug: Executing 'git pull'
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns: 
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns: *** Please tell me who you are.
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns: 
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns: Run
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns: 
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns:   git config --global user.email "you@example.com"
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns:   git config --global user.name "Your Name"
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns: 
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns: to set your account's default identity.
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns: Omit --global to set the identity only in this repository.
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns: 
Notice: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns: fatal: empty ident  <teamcity-agent@tc-agent-03.a.dev.intelliplan.net> not allowed
Error: git pull returned 128 instead of one of [0]
Error: /Stage[main]/Our_buildenv/Rbenv::Compile[1.9.3-p484]/Rbenv::Plugin::Rubybuild[rbenv::rubybuild::teamcity-agent]/Rbenv::Plugin[rbenv::plugin::rubybuild::teamcity-agent]/Exec[rbenv::plugin::update teamcity-agent ruby-build]/returns: change from notrun to 0 failed: git pull returned 128 instead of one of [0]
```