$GEM_BIN_DIR should be added to $PATH

[David Moreau Simard]

Usage of gem binaries is inconsistent.

Here we specify the r10k with the GEM_BIN_DIR path prefix:
https://github.com/openstack/puppet-openstack-integration/blob/5210671dbb6379ef996e35f18dd0de136bdd2b86/functions#L12

Here we don't:
https://github.com/openstack/puppet-openstack-integration/blob/5210671dbb6379ef996e35f18dd0de136bdd2b86/functions#L54

Since $GEM_BIN_DIR is not added to $PATH, this means we can encounter a command not found at line 54 because the full path is not specified.

+ ./install_modules.sh
+ dstat -tcmndrylpg --top-cpu-adv --top-io-adv --nocolor
+ tee --append /var/log/dstat.log
+ '[' -n '' ']'
+ '[' 3 = 4 ']'
+ export PUPPET_BASE_PATH=/etc/puppet
+ PUPPET_BASE_PATH=/etc/puppet
+++ dirname ./install_modules.sh
++ cd .
++ pwd -P
+ export SCRIPT_DIR=/tmp/puppet-openstack
+ SCRIPT_DIR=/tmp/puppet-openstack
+ export PUPPETFILE_DIR=/etc/puppet/modules
+ PUPPETFILE_DIR=/etc/puppet/modules
+ source /tmp/puppet-openstack/functions
+ gem install r10k --no-ri --no-rdoc
+ rm -rf '/etc/puppet/modules/*'
+ install_modules
+ '[' -e /usr/zuul-env/bin/zuul-cloner ']'
+ install_all
+ PUPPETFILE=/tmp/puppet-openstack/Puppetfile
+ r10k puppetfile install -v
/tmp/puppet-openstack/functions: line 53: r10k: command not found

[David Moreau Simard (dmsimard)]

https://review.openstack.org/#/c/329135/