Bug: Non-IEEE-compliant flags/operations in waypoint_manager

[ajshank]

Affects: ros2-devel branch.
Node: waypoint_manager

Brief:
Code uses NaNs and calls std::isnan(), which is erroneous with -ffast-math.

Detail:
The launch parameter init_NEDy defaults to a vector of NaNs (quiet_NaN in std) if left unspecified by the user. This is later checked in std::isnan() to see if user has specified a full and correct list of 4 elements. However, this check will always return false due to -ffast-math (used in CMakeLists.txt) which further enables -fno-signaling-nans and -ffinite-math-only.

Temporary Fix:
Always provide this launch param. To specify an "invalid param", launch with a list of one element.
@ajshank Verified - this works.

Suggested fix:
Don't use -ffast-math? Use some other compliant operation?