fix clock resolution detection

[ktsaou]

Closes: #16710

netdata reads the system's clock resolution to understand the steps it should pause to synchronize data collection.

On some systems clock_getres() is broken. It either returns an error, or it returns invalid values.

Now netdata checks that clock_getres() returns success and also that the the value in usec is bigger than zero and less than 10ms.

If successful, it rounds the clock precision in usec and returns it back. Resolutions smaller than 1 usec are rounded to 1 usec.

If unsuccessful, it returns the default clock resolution of 1ms.

[ilyam8]

The bug was in

netdata/libnetdata/clocks/clocks.c

Lines 52 to 56 in 5d998b9

	static usec_t get_clock_resolution(clockid_t clock) {
	struct timespec ts;
	clock_getres(clock, &ts);
	return ts.tv_sec * USEC_PER_SEC + ts.tv_nsec * NSEC_PER_USEC;
	}

must be ts.tv_nsec / NSEC_PER_USEC;