Update install\update script to use information about region from instance metadata

# Why is this change needed?
Titan zone has a different format of AZ-region

# How does it address the issue?
Extract information about region from region metadata

# How was this tested ?
```
sudo ./install auto
```
OUTPUT:
```
INFO -- : Starting Ruby version check.
INFO -- : Starting update check.
INFO -- : Attempting to automatically detect supported package manager type for
INFO -- : Checking AWS_REGION environment variable for region information...
INFO -- : Checking EC2 metadata service for region information...
INFO -- : Downloading version file from bucket aws-codedeploy-eu-west-1 and key
INFO -- : Downloading version file from bucket aws-codedeploy-eu-west-1 and key
INFO -- : Downloading package from bucket aws-codedeploy-eu-west-1 and key releases/codedeploy-agent-1.0-1.1597.noarch.rpm...
```

```
unset AWS_REGION
sudo ./update auto
```

OUTPUT:
```
INFO -- : Starting Ruby version check.
INFO -- : Starting update check.
INFO -- : Attempting to automatically detect supported package manager type for
INFO -- : Checking AWS_REGION environment variable for region information...
INFO -- : Checking EC2 metadata service for region information...
INFO -- : Downloading version file from BUCKET aws-codedeploy-eu-west-1 and key latest/VERSION...
```

cr https://code.amazon.com/reviews/CR-22605355

Author: Alena Kastsiukavets

bin/install

@@ -5,6 +5,7 @@
 # than 2.0. Testing on multiple Ruby versions is required for
 # changes to this part of the code.
 ##################################################################
+require 'json'
 
 class Proxy
   instance_methods.each do |m|
@@ -198,20 +199,14 @@ EOF
 
   def get_ec2_metadata_region
     begin
-      uri = URI.parse('http://169.254.169.254/latest/meta-data/placement/availability-zone')
-      az = uri.read(:read_timeout => 120)
-      az.strip
+      uri = URI.parse('http://169.254.169.254/latest/dynamic/instance-identity/document')
+      document_string = uri.read(:read_timeout => 120)
+      doc = JSON.parse(document_string.strip)
+      return doc['region'].strip
     rescue
       @log.warn("Could not get region from EC2 metadata service at '#{uri.to_s}'")
       return nil
     end
-
-    if (az !~ /[a-z]{2}-[a-z]+-\d+[a-z]/)
-      @log.warn("Invalid availability zone name: '#{az}'.")
-      return nil
-    else
-      return az.chop
-    end
   end
 
   def get_region

bin/update

@@ -5,6 +5,7 @@
 # than 2.0. Testing on multiple Ruby versions is required for
 # changes to this part of the code.
 ##################################################################
+require 'json'
 
 class Proxy
   instance_methods.each do |m|
@@ -270,20 +271,14 @@ EOF
 
   def get_ec2_metadata_region
     begin
-      uri = URI.parse('http://169.254.169.254/latest/meta-data/placement/availability-zone')
-      az = uri.read(:read_timeout => 120)
-      az.strip
+      uri = URI.parse('http://169.254.169.254/latest/dynamic/instance-identity/document')
+      document_string = uri.read(:read_timeout => 120)
+      doc = JSON.parse(document_string.strip)
+      return doc['region'].strip
     rescue
       @log.warn("Could not get region from EC2 metadata service at '#{uri.to_s}'")
       return nil
     end
-
-    if (az !~ /[a-z]{2}-[a-z]+-\d+[a-z]/)
-      @log.warn("Invalid availability zone name: '#{az}'.")
-      return nil
-    else
-      return az.chop
-    end
   end
 
   def get_region