Check if /etc/swift exists in ring builder

If /etc/swift did not exist, the gluster-swift-gen-builders tool
used to go ahead and create them in current dir.

Change-Id: I1879b959b922de6318ecdff2f16eda12c001ae21
Signed-off-by: Prashanth Pai <ppai@redhat.com>
Merge "Check if /etc/swift exists in ring builder" into icehouse