CSP has capacity factors > 1 when passing shapes

Version Checks (indicate both or one)

• I have confirmed this bug exists on the lastest release of Atlite.

• I have confirmed this bug exists on the current master branch of Atlite.

Issue Description

Depending on how you call csp capacity factors might be wrong

per_unit = True works as intended

capacity_factor=True has issues.

Reproducible Example

import geopandas as gpd
import atlite
import cartopy.io.shapereader as shpreader
import pandas as pd

shp = shpreader.Reader(
    shpreader.natural_earth(
        resolution="10m", category="cultural", name="admin_1_states_provinces"
    )
)
prt_records = list(
    filter(lambda r: r.attributes["iso_3166_2"].startswith("PT"), shp.records())
)
portugal_1 = (
    gpd.GeoDataFrame([{**r.attributes, "geometry": r.geometry} for r in prt_records])
    .rename(columns={"iso_3166_2": "state"})
    .set_index("state")
    .set_crs(4236)
)
portugal_1 = portugal_1.cx[portugal.bounds.minx:,:]
portugal_1.plot()

cutout = atlite.Cutout(
    path="csp-cf-series/test/cutout_csp.nc",  # previous file I had, from the Portugal example
)

csp = cutout.csp(  # I work!
    installation="SAM_solar_tower",
    per_unit=True,
    shapes=portugal_1
)
mean = csp.mean("time").to_series()
portugal_1.plot(column=mean, legend=True)

csp = cutout.csp(  # I don't :(
    installation="SAM_solar_tower",
    capacity_factor=True,
    shapes=portugal_1
)
mean = csp.mean("time").to_series()
portugal_1.plot(column=mean, legend=True)

Expected Behavior

CFs should be correct regardless of how you call for them (although... why are there two calls for the same thing? That's how this type of issue happens...)

Installed Versions

Start at the Cutout.csp entry point and reproduce the Portugal example with installation="SAM_solar_tower", first using per_unit=True and then capacity_factor=True with the provided shapes. Trace why the capacity-factor result differs, and consider the issue resolved when both calls produce correct, consistent capacity factors without values above 1.