[ARM2] Use proper autoload configuration

[phansys]

Q	A
Branch	arm2
Bug fix?	no
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	n/a
License	MIT
Doc PR	n/a

BEFORE:

// vendor/composer/autoload_psr4.php

'' => array($baseDir . '/src', $baseDir . '/gen', $baseDir . '/tests'),

AFTER:

// vendor/composer/autoload_psr4.php

'Microsoft\\Rest\\' => array($baseDir . '/src/Microsoft/Rest', $baseDir . '/tests/Microsoft/Rest'),
'Microsoft\\Azure\\' => array($baseDir . '/gen/Microsoft/Azure', $baseDir . '/tests/Microsoft/Azure'),