Ec2Signer : Modify v4 signer to match latest boto

Previously the port component of the host:port header was stripped
to match what boto (2.6.0->2.9.2) did, however it seems that was a
n error in boto as from boto commit cfaba39 (in 2.9.3) the port is
now appended.

This means that when this fix is used with keystone, APIs which use
keystone to validate ec2 style v4 signatures (e.g the heat cfn API)
will require python-boto >= 2.9.3

Fixes bug #1197553

Change-Id: I4c01e7aef7015a79e6e6263492c51caf3a08e9e4
Merge "Ec2Signer : Modify v4 signer to match latest boto"