The http service name is HTTP

Service names are generally case sensitive in Kerberos implementations (with
the notable exception of Microsoft Active Directory that treats them in a
case-insensitive way). For unknown reasons the service name used for the
http protocol has been historically uppercased. So the examples should use
HTTP otherwise implementors may use http and fail to interoperate with
servers that follow the proper case sensitivity rules for Kerberos principal
names as defined in RFC4120.

Signed-off-by: Simo Sorce <simo@redhat.com>

docs/source/basic-tutorial.md

@@ -43,12 +43,12 @@ Suppose we wanted to refer to an HTTP server on the current host.
 We could refer to it as a *host-based service*, or in the default
 mechanism form (in this case, for krb5):
 
-    >>> server_hostbased_name = gssapi.Name('http@' + FQDN, name_type=gssapi.NameType.hostbased_service)
+    >>> server_hostbased_name = gssapi.Name('HTTP@' + FQDN, name_type=gssapi.NameType.hostbased_service)
     >>> server_hostbased_name
-    Name(b'http@sross', <OID 1.2.840.113554.1.2.1.4>)
-    >>> server_name = gssapi.Name('http/sross@')
+    Name(b'HTTP@sross', <OID 1.2.840.113554.1.2.1.4>)
+    >>> server_name = gssapi.Name('HTTP/sross@')
     >>> server_name
-    Name(b'http/sross@', None)
+    Name(b'HTTP/sross@', None)
     >>>
 
 These are both effectively the same, but if we *canonicalize* both
@@ -75,11 +75,11 @@ Credentials may be acquired for a particular name, or the default set
 of credentials may be acquired.
 
 For instance, suppose that we are writing a server, and wish to
-communicate accept connections as the 'http' service.  We would need
+communicate accept connections as the 'HTTP' service.  We would need
 to acquire credentials as such:
 
-    >>> REALM.addprinc('http/%s@%s' % (FQDN, REALM.realm))
-    >>> REALM.extract_keytab('http/%s@%s' % (FQDN, REALM.realm), REALM.keytab)
+    >>> REALM.addprinc('HTTP/%s@%s' % (FQDN, REALM.realm))
+    >>> REALM.extract_keytab('HTTP/%s@%s' % (FQDN, REALM.realm), REALM.keytab)
     >>> server_creds = gssapi.Credentials(usage='accept', name=server_name)
     >>>