TLS improvements (gophercloud#134)

This commit contains two improvements to the existing TLS module:
1. Now the library ignores the fact the CA certificate can be broken
(if it can't parse it for some reason, it just leaves an empty string
without a notice). From now we raise an error in this case.
2. It tries to prevent some obvious formatting errors in the certificate
like leading and trailing spaces, additional new lines etc.

Author: Fedosin

internal/util.go

@@ -1,6 +1,7 @@
 package internal
 
 import (
+	"bytes"
 	"crypto/tls"
 	"crypto/x509"
 	"fmt"
@@ -50,7 +51,9 @@ func PrepareTLSConfig(caCertFile, clientCertFile, clientKeyFile string, insecure
 		}
 
 		caCertPool := x509.NewCertPool()
-		caCertPool.AppendCertsFromPEM(caCert)
+		if ok := caCertPool.AppendCertsFromPEM(bytes.TrimSpace(caCert)); !ok {
+			return nil, fmt.Errorf("Error parsing CA Cert from %s", caCertFile)
+		}
 		config.RootCAs = caCertPool
 	}