Bump cryptography from 2.1.4 to 2.3 in /apic_fabric_setup

Bumps [cryptography](https://github.com/pyca/cryptography) from 2.1.4 to 2.3.
- [Release notes](https://github.com/pyca/cryptography/releases)
- [Changelog](https://github.com/pyca/cryptography/blob/master/CHANGELOG.rst)
- [Commits](pyca/cryptography@2.1.4...2.3)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

apic_fabric_setup/requirements.txt

@@ -5,7 +5,7 @@ asn1crypto==0.23.0
 certifi==2017.11.5
 cffi==1.11.2
 chardet==3.0.4
-cryptography==2.1.4
+cryptography==2.3
 enum34==1.1.6
 idna==2.6
 ipaddress==1.0.18