Fix backward params in JSON to same values as for forward search

[mmasciov]

No change for iterations without backward search:
http://uaf-10.t2.ucsd.edu/~mmasciov/MkFit_devs/SVA_newJSON_iter4/

For iterations with backward search, re-establishing intended parameters causes minor differences in performance:
http://uaf-10.t2.ucsd.edu/~mmasciov/MkFit_devs/SVA_newJSON_iter9/

However, given that such iterations are not included by default in CMSSW and that differences are anyways minor, I suggest we merge this PR and use the originally intended parameters.

[mmasciov]

Diff in corresponding JSONs only affect bkw parameters. For new JSONs, they match fwd ones, except for conditions on max number of holes, which are still relaxed.
mkFit > diff -y --suppress-common-lines oldJSON/mkfit-phase1-pixelLessStep.json newJSON/mkfit-phase1-pixelLessStep.json
"nlayers_per_seed": 4, | "nlayers_per_seed": 3,
"maxCandsPerSeed": 5, | "maxCandsPerSeed": 2,
"c_drmax_bh": 0.009999999776482582, | "c_drmax_bh": 0.13500000536441803,
"c_dzmax_bh": 0.004999999888241291, | "c_dzmax_bh": 0.13500000536441803,
"c_drmax_eh": 0.009999999776482582, | "c_drmax_eh": 0.13500000536441803,
"c_dzmax_eh": 0.009999999776482582, | "c_dzmax_eh": 0.13500000536441803,
"c_drmax_bl": 0.009999999776482582, | "c_drmax_bl": 0.13500000536441803,
"c_dzmax_bl": 0.004999999888241291, | "c_dzmax_bl": 0.13500000536441803,
"c_drmax_el": 0.014999999664723873, | "c_drmax_el": 0.13500000536441803,
"c_dzmax_el": 0.014999999664723873, | "c_dzmax_el": 0.13500000536441803,
"fracSharedHits": 0.5, | "fracSharedHits": 0.1899999976158142,