(BKR-914) Add workaround for beaker bug BKR-914

The Windows 2012 R2 VMPooler templates were recently updated due to the older
version not populating environment variables correctly.  However this exposed an
issue in Beaker (BKR-914) whereby it's `get_env_var` function was far too loose
in its pattern matching causing multiple lines to be returned for a single env
var.  This then caused newline characters to be injected into the
`~/.ssh/environment` file, which then poluted calls to STDOUT and subsequently
any tests that depended on parsing STDOUT could potentially fail.

This commit adds workarounds to this issue until BKR-914 is fixed and published.
- The output from a `get_env_var` is sanitised and if required, additional regex
  is injected to get the required effect from the `env | grep #{key}` call in
  Beaker
- An existance check is added so that the CommonProgramFiles env var is only
  added if it does not exist.  This avoids modifying the environment
  unncessarily.

This commit can be partially revertted once BKR-914 is resolved and published.

Author: glennsarti

spec/spec_helper_acceptance.rb

@@ -27,8 +27,30 @@
 unless ENV['MODULE_provision'] == 'no'
   agents.each do |agent|
     # Emit CommonProgramFiles environment variable
-    program_files = agent.get_env_var('ProgramFiles').split('=')[1]
-    agent.add_env_var('CommonProgramFiles', "#{program_files}\\Common Files")
+    common_program_files = agent.get_env_var('CommonProgramFiles')
+
+    # Workarounds due to BKR-914
+    #  - newline chars indicate matching more than one env var
+    #  - env var key matching is very loose.  e.g. CommonProgramFiles(x86) can be returned
+    common_program_files = "" if common_program_files.include?("\n")
+    common_program_files = "" unless common_program_files.start_with?("CommonProgramFiles=")
+    #  If the env var is not found use a workaround to inject regex into the grep call
+    common_program_files = agent.get_env_var('^CommonProgramFiles=') if common_program_files == ""
+
+    if common_program_files == ""
+      program_files = agent.get_env_var('PROGRAMFILES')
+
+      # Workarounds due to BKR-914
+      #  - newline chars indicate matching more than one env var
+      #  - env var key matching is very loose.  e.g. ProgramFiles(x86) can be returned
+      program_files = "" if program_files.include?("\n")
+      program_files = "" unless program_files.start_with?("PROGRAMFILES=")
+      #  If the env var is not found use a workaround to inject regex into the grep call
+      program_files = agent.get_env_var('^PROGRAMFILES=') if program_files == ""
+
+      program_files = program_files.split('=')[1]
+      agent.add_env_var('CommonProgramFiles', "#{program_files}\\Common Files")
+    end
 
     # Install Forge certs to allow for PMT installation.
     install_ca_certs(agent)