config: remove dead code in config_validate_namespaces()

config: remove dead code in config_validate_namespaces()

Remove the logically dead code, reported by the Coverity tool:

CID 258280 (#1 of 1): Logically dead code (DEADCODE)dead_error_begin:
Execution cannot reach this statement: last_errno = *__errno_locat....

cg_mount_table[i].mount.path can never be NULL, so remove that check in
the config_validate_namespaces().

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>
(cherry picked from commit aa758d5edc8d043a1e4092ce1ef830bcce3603ae)