Rename getline to fs_getline for fs_mgr

fs_mgr defines its own version of getline and uses it
internally. This leads to a build error if getline is
also defined in bionic, since fs_mgr will see readline
as defined internally.

Rename getline in fs_mgr to a local name (fs_getline)
so that there will no longer be any conflicts.

This is needed it we want to add getline in bionic.

Change-Id: I3a32be71a645e122629802d98ff8f9ab9c419e86
Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>