mgmtd: Fixing code coverity issues in mgmtd

mgmtd: Fixing code coverity issues in mgmtd

Description:
	the following list of coverity issues seen in mgmtd code.
	1. CID 1536832:  Memory - corruptions  (OVERLAPPING_COPY)
	   /mgmtd/mgmt_history.c: 85 in mgmt_history_create_cmt_rec()
	2. CID 1536831:  Error handling issues  (NEGATIVE_RETURNS)
	   /mgmtd/mgmt_be_server.c: 123 in mgmt_be_server_start()
	3. CID 1536830:  Resource leaks  (RESOURCE_LEAK)
	   /mgmtd/mgmt_history.c: 146 in mgmt_history_read_cmt_record_index()
	4. CID 1536829:  Error handling issues  (NEGATIVE_RETURNS)
	   /mgmtd/mgmt_fe_server.c: 123 in mgmt_fe_server_start()
	5. CID 1536828:  Possible Control flow issues  (DEADCODE)
	   /mgmtd/mgmt_txn.c: 1859 in mgmt_txn_get_config()
	6. CID 1536827:  Null pointer dereferences  (NULL_RETURNS)
           /mgmtd/mgmt_ds.c: 526 in mgmt_ds_delete_data_nodes()

Signed-off-by: Rajesh Girada <rgirada@vmware.com>