Description of problem:
if nsslapd-cachememsize set to the number larger than the RAM available, should result in proper error message. 

Steps to Reproduce:
I tried giving a higher value of 1000GB to dn: cn=userRoot,cn=ldbm
database,cn=plugins,cn=config's nsslapd-cachememsize from console,
and the server crashed.

Error ::
>>> ldap_sasl_bind(SIMPLE): Can't contact LDAP server (-1)
>>> < - deleted
>>> > - added
>>> 1,28d0
>>> < # extended LDIF
>>> < #
>>> < # LDAPv3
>>> < # base <cn=userRoot,cn=ldbm database,cn=plugins,cn=config> with
>>> scope baseObject
>>> < # filter: objectclass=*
>>> < # requesting: ALL
>>> < #
>>> <
>>> < # userRoot, ldbm database, plugins, config
>>> < dn: cn=userRoot,cn=ldbm database,cn=plugins,cn=config
>>> < objectClass: top
>>> < objectClass: extensibleObject
>>> < objectClass: nsBackendInstance
>>> < cn: userRoot
>>> < nsslapd-suffix: dc=example,dc=com
>>> < nsslapd-cachesize: -1
>>> < nsslapd-cachememsize: 1073741824
>>> < nsslapd-readonly: off
>>> < nsslapd-require-index: off
>>> < nsslapd-directory: /var/lib/dirsrv/slapd-mgmt12/db/userRoot
>>> < nsslapd-dncachememsize: 10485760
>>> <
>>> < # search result
>>> < search: 2
>>> < result: 0 Success
>>> <
>>> < # numResponses: 2
>>> < # numEntries: 1
>>>
>>> ldap_sasl_bind(SIMPLE): Can't contact LDAP server (-1)
>>>
>>>
>>> [root@mgmt12 scripts]# service dirsrv status
>>> dirsrv mgmt12 dead but pid file exists
>>>
>>> [root@mgmt12 scripts]# tail -f /var/log/dirsrv/slapd-mgmt12/errors
>>> [19/Mar/2013:07:22:31 -0400] memory allocator - calloc of 1 elems of
>>> 268435664 bytes failed; OS error 12 (Cannot allocate memory)
>>> The server has probably allocated all available virtual memory. To solve
>>> this problem, make more virtual memory available to your server, or
>>> reduce
>>> one or more of the following server configuration settings:
>>>   nsslapd-cachesize        (Database Settings - Maximum entries in
>>> cache)
>>>   nsslapd-cachememsize     (Database Settings - Memory available for
>>> cache)
>>>   nsslapd-dbcachesize      (LDBM Plug-in Settings - Maximum cache size)
>>>   nsslapd-import-cachesize (LDBM Plug-in Settings - Import cache size).
>>> Can't recover; calling exit(1).
>>>
>>>
>>> [root@mgmt12 scripts]# cat /proc/meminfo
>>> MemTotal:       16396852 kB
>>> MemFree:        13973916 kB
>>> Buffers:          211892 kB
>>> Cached:          1460572 kB
>>> SwapCached:            0 kB
>>>
>>> #free -m
>>>              total       used       free     shared    buffers    
>>> cached
>>> Mem:         16012       2366      13646          0        206      
>>> 1426
>>> -/+ buffers/cache:        732      15279
>>> Swap:         8071          0       8071
>>>

===>>>It says "Can't contact LDAP server" ..we should display a better
error message on console?
 
Actual results:
Error message says :: "Can't contact LDAP server"

Expected results:
we should display a better error message on console which indicates that RAM is not enough.