krb5conf: wrong parsing when [realms] is a last section

[dpotapov]

Hi,

When [realms] section is last in the config file, it is not detecting last realm:

[libdefaults]
...

[domain_realm]
...

[realms]
 TEST.GOKRB5 = {
  kdc = 10.80.88.88:88
 }
 EXAMPLE.COM = {
        kdc = kerberos.example.com
 }

Test fails:

--- FAIL: TestLoad (0.65s)
	assertions.go:239: 
	Error Trace:	krb5conf_test.go:66
	Error:      	Not equal: 
	            	expected: 2
	            	actual: 1
	Messages:   	Number of realms not as expected